WL#3091: Log tables features

This worklog lists several points missing in the 
current log tables implementation, which were
present in the WL #1019 "SELECT FROM slow_query
logs" spec. Namely:

-- The information shown in the SLOW_LOG and GENERAL_LOG
   tables will be specific to the CURRENT_USER only; that is,
   a user can see only his own entries unless he has SELECT
   privilege on the log table. In the latter case he can see
   all the entries.

-- The old --log options should control location of the
   old-fashioned log files, while CSV tables placement
   should be changed with ALTER TABLE's DATA DIRECTORY
   option. However, DATA DIRECTORY option is currenly
   ignored by ALTER TABLE and ha_tina does not support
   it yet (DATA DIRECTORY works only with CREATE TABLE
   for MyISAM tables at the moment). So, this should be
   fixed.

Another useful extension to the current log tables
implementation is to extend myISAM to be able to
store logs.
  This is being discussed with brian at the moment.

We should also make a decision on the compilation
dependencies. That is, what should be compiled out
and when. Shell we add Configure switch for log
tables? Use a hard depency on CSV? This should be
decided and implemented.