FS-7519: initial version of record_av to record mp4

it generate better compatible mp4 than vlc, so it compatible with quicktime and safari
except that the first few video frames messed up, maybe some pts issue, to be fixed

support float audio, and it can save to webm

src/mod/applications/mod_av/Makefile.am

@@ -5,5 +5,5 @@ mod_LTLIBRARIES = mod_av.la
 mod_av_la_SOURCES  = mod_av.c
 mod_av_la_CFLAGS   = $(AM_CFLAGS)
 mod_av_la_LIBADD   = $(switch_builddir)/libfreeswitch.la
-mod_av_la_LDFLAGS  = -avoid-version -module -no-undefined -shared -lavformat -lavcodec -lavutil -lx264
+mod_av_la_LDFLAGS  = -avoid-version -module -no-undefined -shared -lavformat -lavcodec -lavutil -lswresample -lx264