fate: add a test for the -force_key_frames option.

It broke twice in the last three months due to other changes.

tests/Makefile

@@ -65,6 +65,7 @@ include $(SRC_PATH)/tests/fate/lossless-video.mak
 include $(SRC_PATH)/tests/fate/microsoft.mak
 include $(SRC_PATH)/tests/fate/mp3.mak
 include $(SRC_PATH)/tests/fate/mpc.mak
+include $(SRC_PATH)/tests/fate/options.mak
 include $(SRC_PATH)/tests/fate/pcm.mak
 include $(SRC_PATH)/tests/fate/probe.mak
 include $(SRC_PATH)/tests/fate/prores.mak

tests/fate/options.mak

+FATE_OPTIONS += fate-options-force_key_frames
+fate-options-force_key_frames: tests/data/vsynth2.yuv
+fate-options-force_key_frames: CMD = enc_dec \
+  "rawvideo -s 352x288 -pix_fmt yuv420p" tests/data/vsynth2.yuv \
+  avi "-c mpeg4 -g 240 -qscale 10 -force_key_frames 0.5,0:00:01.5" \
+  framecrc "" "" "-skip_frame nokey"
+
+FATE_FFMPEG += $(FATE_OPTIONS)
+fate-options: $(FATE_OPTIONS)

tests/ref/fate/options-force_key_frames

+654970e7a09ff4869596c2a47e698007 *tests/data/fate/options-force_key_frames.avi
+113320 tests/data/fate/options-force_key_frames.avi
+8f68ad2e602ecd87a3e0c097ba99d773 *tests/data/fate/options-force_key_frames.out.framecrc
+stddev:34363.01 PSNR:  5.61 MAXDIFF:56305 bytes:  7603200/      186