Log Message:
Forgot this in previous commit.

Split out shared parts of PyQt packages to Makefile.common.
I did this so I could get Darwin support which requires a
Mac-specific source.

Also capitalize Qt3 in COMMENT.

I tested a few packages using PyQt running on Mac OS X over remote X11
and it still worked (even though no X11 support, but I guess the Qt3's
X11 works for this).