bug 151388:To add a new compile switch to distinguish Windows and ATK code

patch=john.sun@sun.com r=cls(seawood@netscape.com)
So that we can use
#ifdef ACCESSIBILITY_ATK
//ATK code here
#else
//Windows code here
#endif
to keep the binaries smaller.

configure.in

@@ -4656,6 +4656,10 @@ if test "$MOZ_DEBUG"; then
     AC_DEFINE(MOZ_REFLOW_PERF_DSP)
 fi
 
+if test "$ACCESSIBILITY" -a "$MOZ_ENABLE_GTK2" ; then
+    AC_DEFINE(MOZ_ACCESSIBILITY_ATK)
+fi
+
 # Used for LD_LIBRARY_PATH of run_viewer target
 LIBS_PATH=
 for lib_arg in $NSPR_LIBS $TK_LIBS; do