[Development] Debug category for sql drivers

[Guido Seifert]

Hi,
could have have an sql category for the sql drivers? Currently the postgres driver drives me crazy. :-D
I get constantly a warning: 
	Unable to free statement: ERROR:  prepared statement "qpsqlpstmt_23" does not exist
Does not look like I can do much to remove the cause of this warning in my code.
Therefore I checked, if I can disable it. Unfortunately at least the postgres driver does not use
any categories, but spams default. I really don't want to disable default globally.

Guido