Blacklist abench and bench filters

They must be applied in pairs (start and stop) and only print to
the console. That is not compatible with our avfilter system which
only allows one filter at a time.

Author: bmatherly

src/modules/avformat/blacklist.txt

@@ -1,3 +1,4 @@
+abench
 acopy
 acrossfade
 afifo
@@ -19,6 +20,7 @@ asettb
 astreamselect
 atempo
 atrim
+bench
 channelsplit
 codecview
 copy