CMake: FREEGLUT_REPLACE_GLUT option should not be visible on windows

git-svn-id: https://svn.code.sf.net/p/freeglut/code/trunk@1733 7f0cb862-5218-0410-a997-914c9d46530a
updated list of cmake switches in README.cmake

git-svn-id: https://svn.code.sf.net/p/freeglut/code/trunk@1734 7f0cb862-5218-0410-a997-914c9d46530a
Merge remote-tracking branch 'svn/trunk' into git_master