OpenGL include stuff on OS X.

m4/gltools.m4

@@ -6,7 +6,7 @@ AC_DEFUN([ALBERTA_GLTOOLS_CHECK],
 [AC_REQUIRE([ALBERTA_OPENGL_CHECK])
 AC_LANG_PUSH([C])
 ALBERTA_CHECK_PACKAGE([gltools],[gltools],[glrCreate],[],[${OPENGL_ALL_LIBS}],
-                      [glwin.h glrnd.h],[],[],[optional enabled])
+                      [glwin.h glrnd.h],[],[${OPENGL_ALL_INCLUDES}],[optional enabled])
 if ! test "z${GLTOOLS_LIBS}" = "z"; then
     AC_MSG_CHECKING([for gltools version])
     ac_al_save_CPPFLAGS="${CPPFLAGS}"