Added Thierry's change to include sys/param.h. This lets us pick out version

Added Thierry's change to include sys/param.h.  This lets us pick out version
numbers for OS releases corresponding to system headers.

I modified it to also work with NetBSD; I cannot confirm if it is safe with
any other systems, so it remains protected by a #if.

git-svn-id: svn+ssh://svn.code.sf.net/p/freeglut/code/trunk/freeglut/freeglut@262 7f0cb862-5218-0410-a997-914c9d46530a