LP #691404: log-slow-admin-statements is not in show variables

**Reported in Launchpad by Peter Zaitsev last update 06-10-2011 21:53:36

Ensure --log-slow-admin-statements is:

1) added to SHOW VARIABLES
2) can be set online (global variable is enough)
3) ensure it logs ALL statements.

The former is important in our performance analyzes we often assume we have complete picture of queries running on server in the log, it is not unless this option is enabled and we need to ensure it enables it for everything.