export thebes symbols from libxul. bug 388663. r=vlad

gfx/thebes/public/gfxTypes.h

@@ -46,9 +46,7 @@
  */
 typedef double gfxFloat;
 
-#if defined(MOZ_ENABLE_LIBXUL) || defined(MOZ_STATIC_BUILD)
-# define THEBES_API
-#elif defined(IMPL_THEBES)
+#if defined(IMPL_THEBES)
 # define THEBES_API NS_EXPORT
 #else
 # define THEBES_API NS_IMPORT