build: compile with -D__DARWIN_64_BIT_INO_T on OS X

Fixes a struct stat size mismatch on 64 bits machines that made Node crash with
a EXC_BAD_ACCESS on startup.

Fixes #2061 for gyp builds. Solution proposed by Paddy Byers.

common.gypi

@@ -128,6 +128,7 @@
         ],
       }],
       ['OS=="mac"', {
+        'defines': ['__DARWIN_64_BIT_INO_T=1'],
         'xcode_settings': {
           'ALWAYS_SEARCH_USER_PATHS': 'NO',
           'GCC_CW_ASM_SYNTAX': 'NO',                # No -fasm-blocks