"set optimizer_switch to e or d causes invalid memory writes/valgrind warnings":
due to prefix support, the argument "e" was overwritten with its full value
"engine_condition_pushdown", which caused a buffer overrun.
This was wrong usage of find_type(); other wrong usages are fixed here too.
Please start reading with the comment of typelib.c.

client/mysqldump.c:
  A bug: find_type() expects a bitmap as 3rd argument
  (each bit is a flag controlling a behaviour of the function);
  here it was instead passed the length of the string to search!
  That could give random behaviour of find_type()
  depending on the string.
  We rather need to pass a correct flag to find_type().
  The correct flag is FIND_TYPE_BASIC (0).
  Flag 8 is not needed as buff cannot have a comma (see how buff is filled).
  Flag 1 looks like a superfluous restriction.
  Flag 4 is not user-friendly (why use
  --compatible=2 rather than --compatible=mysql40 ?, and
  we probably not commit to "2" always meaning "mysql40"
  until the end of times).
include/mysql.h.pp:
  This isn't a problematic API change as we go from char* to const char*:
  existing code will run unchanged.
include/typelib.h:
  named constants. Not an enum to not significantly change
  the declaration of find_type() which would be an API change
  (typelib.h is included in mysql.h).
mysql-test/r/mysqldump.result:
  correct result (see the two requested modes in SQL_MODE)
mysql-test/suite/sys_vars/t/optimizer_switch_basic.test:
  test for BUG#59894. The second SET used to crash.
mysql-test/t/mysqldump.test:
  we had no test for multiple modes in --compatible, which is
  supported according to --help
mysys/typelib.c:
  Fix for BUG#59894. parse_name() is asked to match "e" with a row
  of the TYPELIB (the TYPELIB lists permitted flags of optimizer_switch;
  and comes from optimizer_switch_names[] of sys_vars.cc).
  find_type() is capable of supporting prefixes, but if it is not
  passed flag 2 in third argument, it will overwrite its first
  argument (the string to search for) with the complete name,
  here overwriting "e" with "engine_condition_pushdown". But
  as this "e" was a buffer allocated in an Item, it was not big
  enough to host the longer name, thus the crash.
  We don't need to know the complete flag's name; the output used
  from find_type() is just the flag's number (== function's return
  code). So we can pass flag 2 to find_type() in parse_name().
  After doing this fix and the other fixes in this patch, all usages
  of find_type() were using flag 2; in most usages the string to search for,
  is not guaranteed to be long enough to host the complete name
  (it is either directly from argv, or from alloc_root/my_malloc
  done in an earlier call).
  Thus, flag 2 is here made implicit: callers need not pass it anymore,
  it is always automatically turned on.
  This allows to eliminate an oddity: parse_name() took a const char**,
  and then removed "const" before calling find_type(), which could
  theoretically modify the pointed data, thus lying on constness.
  Last, constants for find_type() are now named.
sql-common/client.c:
  Two bugs:
  1) The enum was not in sync with the array (due to a bad porting of WL 1054;
  the extra OPT_ values are about options present in 5.1 and deleted in 5.5);
  added a compile_time_assert() to make sure this doesn't happen again
  2) find_type() was writing past the end of opt_arg; as opt_arg was allocated
  with alloc_root() with no extra space, this was an overrun; it could be seen
  when
  ** building with -DWITH_VALGRIND -DHAVE_purify -DEXTRA_DEBUG
  ** making execution go through the faulty code; this faulty
  code is executed only if the client asks to read a configuration
  file like this:
    mysql_options(mysql, MYSQL_READ_DEFAULT_FILE, "/tmp/cnf.cnf");
  so by adding such line to the start of mysql_client_test.c::client_connect(),
  we could see the valgrind warning:
  ==30548== Invalid write of size 1
  ==30548==    at 0x4C2624C: strcpy (mc_replace_strmem.c:303)
  ==30548==    by 0x48DC29: find_type (typelib.c:120)
  ==30548==    by 0x465686: mysql_read_default_options (client.c:1344)
  ==30548==    by 0x46830F: mysql_real_connect (client.c:2971)
  ==30548==    by 0x409339: client_connect (mysql_client_test.c:331)
  ==30548==    by 0x463A7F: main (mysql_client_test.c:19902)
  ==30548==  Address 0x61875ad is 0 bytes after a block of size 29 alloc'd
  ==30548==    at 0x4C25153: malloc (vg_replace_malloc.c:195)
  ==30548==    by 0x49BFF1: my_malloc (my_malloc.c:38)
  ==30548==    by 0x49C65C: alloc_root (my_alloc.c:166)
  ==30548==    by 0x48EF97: handle_default_option (default.c:381)
  ==30548==    by 0x49068C: search_default_file_with_ext (default.c:992)
  ==30548==    by 0x48F929: search_default_file (default.c:670)
  ==30548==    by 0x48EDC4: my_search_option_files (default.c:312)
  ==30548==    by 0x48F4B1: my_load_defaults (default.c:576)
  ==30548==    by 0x46517A: mysql_read_default_options (client.c:1207)
  ==30548==    by 0x46830F: mysql_real_connect (client.c:2971)
  ==30548==    by 0x409339: client_connect (mysql_client_test.c:331)
  ==30548==    by 0x463A7F: main (mysql_client_test.c:19902)
  This is fixed by having find_type() not overwrite anymore.
sql/sql_help.cc:
  cast not needed anymore.
sql/table.cc:
  cast not needed anymore.

The crash happens because Item_cache which is result
holder for Item_subselect can't correctly convert
a DATETIME value from string to int representation.
The fix is to disable constant item convertion for
subselect(partial rollback of bug52157 fix).


mysql-test/r/type_date.result:
  test case
mysql-test/t/type_date.test:
  test case
sql/item_cmpfunc.cc:
  disable constant item convertion for subselects.

An after-fix to workaround different metadata in "mtr --ps" output.

batch_readline_init() was modified - make check for 
type of file for input stream unless target platform
is WINDOWS since on this platform S_IFBLK is undefined.

Reverse DNS lookup of "localhost" returns "broadcasthost" on Snow Leopard (Mac), and NULL on most others.
Simply ignore the output, as this is not an essential part of UDF testing.

batch_readline_init() was modified - return an error
if the input source is a directory or a block device.

This follow-up is necessary because on some platforms,
such as Solaris, call to read() from directory may be
successful.

Resolved an innodb conflict thanks to vasil.

Test failed on a certain Linux platform in automated environment. It turns out that this platform has an old version of Perl modules DBI and DBD::mysql installed, as well as the OS itself being relatively old.
Allowing error code 11 to be returned from mysqlhotcopy on expected error seems harmless and will make the test pass also with older libraries.

Removed the collections for mysql-5.1-bugteam. Removed 1st from weekly. This is part of default suites

Removed the collections for mysql-5.1-bugteam. Removed 1st from weekly. This is part of default suites