splittiln common client's parts

Here is another pack of changes about gathering common client code in
sql-common/client.c.
Now i symlink the client.c from sql/ and libmysql/. These directories
have client_settings.h files to be included to client.c. It contains
defines and declarations to compile client.c in appropriate manner.
Also i've added include/sql_common.h, containing declarations of what
is exported from client.c

I removed as many #ifdef-s from client.c as i dared to. I think it's better
push it with some extra #ifdef-s now (of course, if everythihg besides it is
ok) so other people can check the code.

into deer.(none):/home/hf/work/mysql-4.1.emb_bind

into eagle.mysql.r18.ru:/home/vva/work/NEW_HELP/4.1.clear

  character_set_connection new variable

character_set_database was added
Code optimization: reuse more code for all character sets variables

SELECT CAST(_latin1'string' AS CHAR CHARACTER SET latin2)

  bug #521 fix: ('3'='4')  was true in cp1250_czech_ci

./configure --with-charset=latin1 --with-collation=latin1_danish_ci

  ifdef wrong structure has been fixed

into sanja.is.com.ua:/home/bell/mysql/bk/work-4.1

   compile problems

Fixed new bug when reading field types

into narttu.mysql.fi:/my/mysql-4.1

  Changes according to CHARSET_INFO structure

  utf8 was not marked as compiled

into narttu.mysql.fi:/my/mysql-4.1

into mashka.mysql.fi:/home/my/mysql-4.1-narttu

  Remove accidenatlly committed debug printfs when query cache is used
sql_update.cc, sql_load.cc, sql_insert.cc, sql_delete.cc:
  For the transactional query cache algorithm to work we must invalidate the query cache in INSERT/DELETE/UPDATE before writing to the binlog or calling ha_autocommit_... Note that binlog writing may also call commit. The crucial thing is that the transaction which modified data must not be committed BEFORE the query cache is invalidated.

into mashka.mysql.fi:/home/my/mysql-4.1-narttu

ctype_ucs2 and ctype_ujis were skipped in mistake

  cp1250_czech_ci was displayed even when not compiled-in in mistake.

  Character set in this test results was displayed dispite the fact that the table has the same character set

  c
Index.xml:
  Collation names form lati7 were mixed