fate: add synthetic swresample resampling tests

this is based on libavresample.mak

These tests do not depend on external samples
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

tests/Makefile

@@ -110,6 +110,7 @@ include $(SRC_PATH)/tests/fate/libavdevice.mak
 include $(SRC_PATH)/tests/fate/libavformat.mak
 include $(SRC_PATH)/tests/fate/libavresample.mak
 include $(SRC_PATH)/tests/fate/libavutil.mak
+include $(SRC_PATH)/tests/fate/libswresample.mak
 include $(SRC_PATH)/tests/fate/lossless-audio.mak
 include $(SRC_PATH)/tests/fate/lossless-video.mak
 include $(SRC_PATH)/tests/fate/microsoft.mak