CMake housekeeping.

* Remove CMakeParseArguments.cmake to use the version that ships with CMake.
* Remove FindPackageHandleStandardArgs.cmake to use the version that ships
  with CMake.
* Remove FindPythonLibs.cmake to use the version that ships with CMake.
* Edit FindPythonInterp.cmake to use the stock CMake version of
  FindPackageHandleStandardArgs.cmake since the local version was removed.