MySQL for Python MySQLdb-SVN

More serious restructuring and cleaning, especially in the handling
of result sets. All tests pass.

This passes all test, yet is still broken and ugly in many ways.
However, a lot of ugliness has been removed.

Added a simple_fetch_row() to the result object that simply returns one row
as a tuple of strings (or None for NULL values). Result objects are also
now iterators which internally use simple_fetch_row().

Check in some old changes

Back-port unsigned long kill unpack fix from 1.2br.

Unpack kill argument into an unsigned long correctly.

SF bug #2902635

show_warnings was renamed show_warnings (bug 2796727)

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.

simplify using PyString_FromFormat

Defer adding references until after all our C calls so we can avoid having
to decrement them if we bail out early.

Fixes bug 2811033.