handle cmake policies

fix compile warning
Merge branch 'master' of git://github.com/ElektraInitiative/libelektra
obviously include is not including in CMake..
fix cmake error (include missing file)
Merge branch 'master' of git://github.com/ElektraInitiative/libelektra
fix MinGW automatic -ansi options inclusion

... which will emit error messages like:
error: '::swprintf' has not been declared

just to start compiling