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mostly useless and mostly superseded by the coloured variant,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 5a772cbf7d490bc9cffa6c2f97c5fd2d3e30f068)

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()