BUG#39325 Server crash inside MYSQL_LOG::purge_first_log halts replicaiton

The patch reverses the order of the purging and updating events for log and
relay-log.info/index files respectively.

This solves the problem of having holes caused by crashes happening between updating
info/index files and purging logs.

This patch also contains an aditional test case for testing the crashing before purge logs.
      
NOTE1: This is a combined patch for BUG#38826 and BUG#39325. This patch is based on
bugteam tree and takes into account reviewers suggestions.

NOTE2: Merge from 5.0-bugteam

BUG#39325 Server crash inside MYSQL_LOG::purge_first_log halts replicaiton

The patch reverses the order of the purging and updating events for log and relay-log.info/index files respectively.
This solves the problem of having holes caused by crashes happening between updating info/index files and purging logs.

NOTE: This is a combined patch for BUG#38826 and BUG#39325. This patch is based on bugteam tree and takes into account reviewers suggestions.

The bug is repeatable with latest(1.0.1) InnoDB plugin on Linux, Win,
If MySQL is compiled with valgrind there are errors about
using of uninitialized variable(orig_table).
The fix is to set field->orig_table correct value.

Reason for the failing test was that "SELECT count(*) from mysql.general_log;" was not always
the same number. That was fixed by "...count(*)>4..." as the minimal fulfilled condition.
As Bug 35371 was fixed the testcase with "log_output = 'FILE'" was enabled and changed to have
always the same result.

enable uncacheable flag if we update a view with check option
and check option has a subselect, otherwise, the check option
can be evaluated after the subselect was freed as independent
(See full_local in JOIN::join_free())

set DATE|DATETIME value to 0 if ALLOW_INVALID_DATES sql_mode is not enabled.

extended perror to enable printing of Win32 system errors

(no conflicts)

We pretended that TIMEDIFF() would always return positive results;
this gave strange results in comparisons of the TIMEDIFF(low,hi)<TIME(0)
type that rendered a negative result, but still gave false in comparison.
We also inadvertantly dropped the sign when converting times to
decimal.

CAST(time AS DECIMAL) handles signs of the times correctly.
TIMEDIFF() marked up as signed. Time/date comparison code switched to
signed for clarity.

symlink.test failed when run in an environment that has mysql-test/var
symlinked to elsewhere, e.g. a memory file system. This is the case
when running mysql-test-run --mem.

In this case the server does not detect that the directory specified
with a DATA/INDEX DIRECTORY clause is within its data home directory.
This problem was reported as Bug#39277 (Creation of table with data
and/or index files in data home directory succeeds). It was decided
that it will not be fixed in 5.1. Hence, the current behavior is
accepted for 5.1. It will be fixed in 6.0 though.

Fixed the test case so that it works in both environments. 1. When no
symbolic link is involved, the server notices that the data/index
directory is in its data hone directory and rejects the CREATE/ALTER
TABLE statement. 2. When the data home directory is symlinked, it
does not notice the problem and executes the statement sucessfully.