wip

NOTES
 - cannot locate the system Python framework for unknown reasons
 - the CPPFLAGS bit is necessary to compile with Homebrew python, but
   if Homebrew python isn't installed, then macvim won't compile (at
   all, even without python support) *with* it
 - compiles against Homebrew python alone OK
 - o_O when compiled against Homebrew python and python 3:
     :py import sys; print(sys.prefix)
     /usr/local/Cellar/python/2.7.6_1/Frameworks/Python.Framework/Versions/2.7
     :py3 import sys; print(sys.prefix)
     SEGFAULT

   however,

     :py3 import sys; print(sys.prefix)
     /usr/local/Cellar/python/3.4.0_1/Frameworks/Python.Framework/Versions/3.4
     :py import sys; print(sys.prefix)
     /usr