Only try to translate PYTHONPATH for windows/cygwin.  It's not implemented for cross compilation.

git-svn-id: http://svn.boost.org/svn/boost/trunk@84908 b8fc166d-592f-0410-95f2-cb63ce0dd405
Added default for parameter to try to satisfy VC++

git-svn-id: http://svn.boost.org/svn/boost/trunk@84909 b8fc166d-592f-0410-95f2-cb63ce0dd405