Additional Leopard-related project changes (Synergy, f2d4f39)

The change to GCC 4.0 from commit da40c00 wasn't really complete because it did not include changes to the "build rules", although they were in my local working copy. I then accidentally threw away those changes by doing a "git checkout -f master" (was puzzled as to why merely "git checkout master" didn't work; was bailing with "not uptodate. Cannot merge."; I had forgotten that my local fix_deprecation_warnings branch was actually forked from my leopard_conversion branch and not from master; in fact, I'd forgotten that there even was a leopard_conversion branch!; this will teach me to use "git branch" and "git show-branch" more often to remind me where I actually am).

Signed-off-by: Greg Hurrell <greg@hurrell.net>