ABORT_SERVER

Problem:
=======
When binlog_error_action == ABORT_SERVER then server writes
to error log:

[ERROR] An error occured during flushing cache to file.
'binlog_error_action' is set to 'ABORT_SERVER'.
Hence aborting the server

and calls _exit(MYSQLD_FAILURE_EXIT);

Calling _exit means no core-dump is possible. Therefore
nobody knows what was going on.

Analysis:
========
Initially binlog_error_action was added for a special case
where binary logging was not possible due to a readonly
file system or diskfull. In these cases it was not possible
to generate core file and the only option was to call
_exit. But over a period of time the usage of
binlog_error_action has increased and we started using
binlog_error_action for handling other critical errors as
well. Since _exit command doesn't generate are core-dump
users will not get to know what went wrong with the system.
Hence the _exit has to be replaced with abort() call.

Fix:
===
Replaced "_exit" with "abort()" call at all places. Improved
code comments. Existing code was using "my_error" function
call to push error to client and "sql_print_error" to print
error server error log. Printing to client and to server
error log can be achieved with single "my_error" function
call with some additional flags. Implemented those changes.