Adding lines to build the new gtkxtbin library for implementing legacy

plugin support on Linux.  This is part of bug #31012.
-r=blizzard

Makefile.in

@@ -64,6 +64,10 @@ ifndef MOZ_NATIVE_JPEG
 DIRS		+= jpeg
 endif
 
+ifdef MOZ_ENABLE_GTK
+DIRS           += widget/src/gtksuperwin widget/src/gtkxtbin
+endif
+
 DIRS		+= \
 		widget/timer \
 		include \

allmakefiles.sh

@@ -458,6 +458,7 @@ widget/src/beos/Makefile
 widget/src/build/Makefile
 widget/src/gtk/Makefile
 widget/src/gtksuperwin/Makefile
+widget/src/gtkxtbin/Makefile
 widget/src/motif/Makefile
 widget/src/motif/app_context/Makefile
 widget/src/photon/Makefile