support my.cnf reading

[9ydss63a]

this patch can read my.cnf and my.cnf group.

ex.
mysql://localhost/test?mycnfgroup=zdb&mycnffile=/tmp/myz.cnf

reads /tmp/myz.cnf and [zdb] group.

[Tildeslash]

OK, thanks. We won't add this "patch" as it has several issues, but the ability to read credentials from config can be useful for some, sometime