MySQL for Python MySQLdb-SVN

Defer incrementing reference to the decoder stack until later so we don't have to
dec-ref if an error happens. Merge of change 630 on 1.2br.

Reimplement MySQL->Python type conversion in C; much simpler and easier to deal with now. Hey, all my tests pass, so I guess that means I need to write some more tests.

make things a little cleaner by moving to a src directory for the C code