PythonApplyPatches: Use upper & lowercase *_FOUND vars when locating git & patch
PythonApplyPatches: Use upper & lowercase *_FOUND vars when locating git & patch

This allows to support version of CMake < 3.3 that do not have a version
of the FindPackageHandleStandardArgs (see kitware/cmake@d1a6d15) setting
both variables.

Fixes #218

python-cmake-buildsystem/python-cmake-buildsystem,adrianbroher/python-cmake-buildsystem,davidsansome/python-cmake-buildsystem