Fixe error 'error: garbage collection is no longer supported' with Xcode Version 5.1 (5B130a)
GCC_ENABLE_OBJC_GC_macosx = NO
Fixe error 'error: garbage collection is no longer supported' with Xcode Version 5.1 (5B130a)

Use the latest fix from the original webkit.org sources
Merge pull request #487 from wolfviking0/master_r165450

Fixed error 'error: garbage collection is no longer supported'

Reviewed by Antonio.