Slight style improvements. Two rules of thumb that are almost always

Slight style improvements.  Two rules of thumb that are almost always
good to apply:

 * Don't write a == CONST.  Instead, write CONST == a.  Or, more generally
   (in C like languages): Avoid putting an lvalue on the left-hand side of
   an == comparison.  (For consistancy, I try to avoid lvalues on the left-
   hand side of any comparison---but == is the most notorious.)

   (An "lvalue" is a value that can safely go on the left side of an
   "=" assignment, of course.  (^&)

 * Do not write
       if( !condition )
           return;
       other_thing;
       return;

   (See page 18 of K&P's _The Elements of Programming Style_.)

   Instead, it is better to just write:

       if( condition )
           other_thing;
       return;

   There are times when sacrificing structured programming (e.g., via
   multiple return statements) is okay.  But, here, there is no apparent
   gain---indeed, there seems only loss---in the non-structured code.

git-svn-id: svn+ssh://svn.code.sf.net/p/freeglut/code/trunk/freeglut/freeglut@308 7f0cb862-5218-0410-a997-914c9d46530a