OS X: PYTHON_CFLAGS & PYTHON_LIBS (--enable-python=system)

Use $FRAMEWORKSHOME instead of /Developer/SDKs/MacOSX${with_macosx_sdk}.sdk/System/Library/Frameworks.

As of Xcode 5.0, Python has been moved outside the SDK, so it doesn't provide the Python framework.
Now we have to use common unix parameters unlike older versions of Xcode.
It is described in the technical note TN2328.

Change-Id: Ib2a010e7c3839a8906acb2453c90ef2bd2f258d7
Reviewed-on: https://gerrit.libreoffice.org/9926
Reviewed-by: Norbert Thiebaud <nthiebaud@gmail.com>
Tested-by: Norbert Thiebaud <nthiebaud@gmail.com>