Removed LoadableCategory because it is not needed anymore

As a note, -all_load and -force_load should no longer be necessary on LLVM in Xcode 4.2 and higher: stackoverflow.com/a/7942924/19679 . At one point, they were required due to a linker bug, but that issue has since been resolved in the latest versions of LLVM. You should be able to drop the linker flags other than -ObjC