- iOS targets were not using the precompiled header (prefix) file
- Fixed self-referential GCC_PROCESSOR_DEFINITIONS
- Removed PPC-specific build flags, since we can't build for PPC in Xcode 6
- Added KDefinitions.h to precompiled header file since it is included in 77% of source files
- Fixed compiler warning in ffi_common.h caused by moving KDefinitions.h to precompiled header