SF patch 508730 CGIHTTPServer execfile should save cwd

UNTESTED!!!

This simple two-line patch has been sitting on SF for more than 2 years.
I'm guessing it's because nobody knows how to test it -- I sure don't.
It doesn't look like you can get to this part of the code on Unixish
or Windows systems, so the "how to test it?" puzzle has more than one
part.  OTOH, if this is dead code, it doesn't matter either if I just
broke it <wink>.