Some fixes for linking Python on Windows.

CMake FindPythonLibs will look for multiple versions of Python
including both debug and release, and build up a list such as
(debug <debugpath> optimized <optimizedpath>).  This confuses
the logic we have in CMake to copy the correct python dll to
the output directory so that it need not be in your system's PATH.

To alleviate this, we manually split this list and extract out
the debug and release versions of the python library, and copy
only the correct one to the output directory.

llvm-svn: 226679