AA: drop priority to zero

This plugin can cause VLC to crash or exit prematurely. Sicne it is
mostly useless and mostly superseded by the coloured variant,
lets disable it unless explicitly selected.

This should fix LP#971106.
(cherry picked from commit 5a772cbf)

modules/video_output/aa.c

@@ -57,7 +57,7 @@ vlc_module_begin()
     set_category(CAT_VIDEO)
     set_subcategory(SUBCAT_VIDEO_VOUT)
     set_description(N_("ASCII-art video output"))
-    set_capability("vout display", 10)
+    set_capability("vout display", /*10*/0)
     add_shortcut("aalib")
     set_callbacks(Open, Close)
 vlc_module_end()