LICENSE: Document all GPL files

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

LICENSE

@@ -14,17 +14,27 @@ configure to activate them. In this case, FFmpeg's license changes to GPL v2+.
 Specifically, the GPL parts of FFmpeg are
 
 - libpostproc
+- libmpcodecs
 - optional x86 optimizations in the files
   libavcodec/x86/idct_mmx.c
+- libutvideo encoding/decoding wrappers in
+  libavcodec/libutvideo*.cpp
 - the X11 grabber in libavdevice/x11grab.c
+- the swresample test app in
+  libswresample/swresample-test.c
 - the texi2pod.pl tool
 - the following filters in libavfilter:
     - vf_blackframe.c
     - vf_boxblur.c
+    - vf_colormatrix.c
     - vf_cropdetect.c
     - vf_delogo.c
     - vf_hqdn3d.c
+    - vf_mp.c
+    - vf_super2xsai.c
+    - vf_tinterlace.c
     - vf_yadif.c
+    - vsrc_mptestsrc.c
 
 There are a handful of files under other licensing terms, namely: