Modified the menus to refer to {border} rather than {FREEGLUT_MENU_BORDER},

Modified the menus to refer to {border} rather than {FREEGLUT_MENU_BORDER},
in fghDisplayMenuBox().  The local variable was already defined and used
for some purposes, so we might as well use it throughout.  It does serve
to shorten and clarify the code a bit---though I have mixed feelings about
creating aliases that way.

Still, the variable already existed and was already used in places.  (We
could even move it into the freeglut state, or make it a {const static}
value...)

Oh well.  Stuff to ponder.

git-svn-id: svn+ssh://svn.code.sf.net/p/freeglut/code/trunk/freeglut/freeglut@328 7f0cb862-5218-0410-a997-914c9d46530a