Properly escape Xcode defines containing ' 
Properly escape Xcode defines containing ' 

BUG=gyp:257
TEST=python gyptest.py -a -f xcode,make

Patch by Jan Svarovsky <honza@google.com>
Review URL: https://codereview.chromium.org/18621003/

old8xp/gyp_from_google,old8xp/gyp_from_google,old8xp/gyp_from_google,old8xp/gyp_from_google,old8xp/gyp_from_google