[ffvpx] Update ffvp9/ffvp8 to 3.4.2-release

Structure of code was slightly modified so that it should be no longer necessary to re-generate the config_*.h files, greatly simplifying the resync process in the future.

media/ffvpx/libavcodec/moz.build

@@ -16,7 +16,11 @@ SOURCES += [
     'avpacket.c',
     'avpicture.c',
     'bitstream.c',
+    'bitstream_filter.c',
+    'bitstream_filters.c',
+    'bsf.c',
     'codec_desc.c',
+    'decode.c',
     'dummy_funcs.c',
     'flac.c',
     'flac_parser.c',
@@ -28,6 +32,7 @@ SOURCES += [
     'imgconvert.c',
     'log2_tab.c',
     'mathtables.c',
+    'null_bsf.c',
     'options.c',
     'parser.c',
     'profiles.c',
@@ -48,10 +53,16 @@ SOURCES += [
     'vp8dsp.c',
     'vp9.c',
     'vp9_parser.c',
+    'vp9block.c',
+    'vp9data.c',
     'vp9dsp.c',
     'vp9dsp_10bpp.c',
     'vp9dsp_12bpp.c',
     'vp9dsp_8bpp.c',
+    'vp9lpf.c',
+    'vp9mvs.c',
+    'vp9prob.c',
+    'vp9recon.c',
     'xiph.c'
 ]