Compiling with -ansi makes a lot of important POSIX (standard UNIX) facilities

Compiling with -ansi makes a lot of important POSIX (standard UNIX) facilities
unavailable. This was masked until recently by an incorrect conditional in the
CMakeLists.txt file, that looked like it would use -ansi on anything other than
android, but it didn't actually use it anywhere. As soon as that was fixed, and
-ansi started being used, build broke on linux.

The intention of the -ansi flag was to help catch portability-reducing mistakes
in the code, so instead of removing it completely I used -pedantic in its place,
which produces a lot of warnings for not strictly ISO/ANSI compliant code that
relies on compiler-specific features.

git-svn-id: svn+ssh://svn.code.sf.net/p/freeglut/code/trunk/freeglut/freeglut@1681 7f0cb862-5218-0410-a997-914c9d46530a