Remove utils_macosx.*: we don't use the autorelease wrapper function in it anymore.
Adding more entries in the git ignore files.
Update the Xcode project file:
Use the 10.6 SDK for x86_64.
Use the 10.4 SDK for 32-bit builds, except for SheepShaver which uses NSInteger.
Set the deployment target for 32-bit builds to 10.4.
Use gcc 4.2 on x86_64, and 4.0 on 32-bit.