avfilter/asubprocess: initial incomplete version of subprocess filter

Signed-off-by: Stefan Westerfeld <stefan@space.twc.de>

libavfilter/Makefile

@@ -110,6 +110,7 @@ OBJS-$(CONFIG_ASR_FILTER)                    += af_asr.o
 OBJS-$(CONFIG_ASTATS_FILTER)                 += af_astats.o
 OBJS-$(CONFIG_ASTREAMSELECT_FILTER)          += f_streamselect.o framesync.o
 OBJS-$(CONFIG_ASUBBOOST_FILTER)              += af_asubboost.o
+OBJS-$(CONFIG_ASUBPROCESS_FILTER)            += af_asubprocess.o
 OBJS-$(CONFIG_ASUBCUT_FILTER)                += af_asupercut.o
 OBJS-$(CONFIG_ASUPERCUT_FILTER)              += af_asupercut.o
 OBJS-$(CONFIG_ASUPERPASS_FILTER)             += af_asupercut.o

libavfilter/allfilters.c

@@ -101,6 +101,7 @@ extern const AVFilter ff_af_asubcut;
 extern const AVFilter ff_af_asupercut;
 extern const AVFilter ff_af_asuperpass;
 extern const AVFilter ff_af_asuperstop;
+extern const AVFilter ff_af_asubprocess;
 extern const AVFilter ff_af_atempo;
 extern const AVFilter ff_af_atilt;
 extern const AVFilter ff_af_atrim;