fate: add one select filter test

This test selects alternate frames from input.

tests/fate/filter-video.mak

@@ -40,6 +40,10 @@ FATE_FILTER_VSYNTH-$(CONFIG_OVERLAY_FILTER) += fate-filter-overlay
 fate-filter-overlay: tests/data/filtergraphs/overlay
 fate-filter-overlay: CMD = framecrc -c:v pgmyuv -i $(SRC) -c:v pgmyuv -i $(SRC) -filter_complex_script $(TARGET_PATH)/tests/data/filtergraphs/overlay
 
+FATE_FILTER_VSYNTH-$(CONFIG_SELECT_FILTER) += fate-filter-select-alternate
+fate-filter-select-alternate: tests/data/filtergraphs/select-alternate
+fate-filter-select-alternate: CMD = framecrc -c:v pgmyuv -i $(SRC) -filter_script $(TARGET_PATH)/tests/data/filtergraphs/select-alternate
+
 FATE_FILTER_VSYNTH-$(call ALLYES, SETPTS_FILTER  SETTB_FILTER) += fate-filter-setpts
 fate-filter-setpts: tests/data/filtergraphs/setpts
 fate-filter-setpts: CMD = framecrc -c:v pgmyuv -i $(SRC) -filter_script $(TARGET_PATH)/tests/data/filtergraphs/setpts

tests/filtergraphs/select-alternate

+select=not(mod(n\,2))

tests/ref/fate/filter-select-alternate

+#tb 0: 1/25
+0,          0,          0,        1,   152064, 0x05b789ef
+0,          2,          2,        1,   152064, 0x9dddf64a
+0,          4,          4,        1,   152064, 0x4de3b652
+0,          6,          6,        1,   152064, 0xe20f7c23
+0,          8,          8,        1,   152064, 0x1f1b8026
+0,         10,         10,        1,   152064, 0x02344760
+0,         12,         12,        1,   152064, 0xc711ad61
+0,         14,         14,        1,   152064, 0x52a48ddd
+0,         16,         16,        1,   152064, 0x8e364e18
+0,         18,         18,        1,   152064, 0xf25f6acc
+0,         20,         20,        1,   152064, 0xfc7bf570
+0,         22,         22,        1,   152064, 0x445d1d59
+0,         24,         24,        1,   152064, 0xce09f9d6
+0,         26,         26,        1,   152064, 0x43d796b5
+0,         28,         28,        1,   152064, 0x76d2a455
+0,         30,         30,        1,   152064, 0x0f9d6aca
+0,         32,         32,        1,   152064, 0xd766fc8d
+0,         34,         34,        1,   152064, 0x7fea4378
+0,         36,         36,        1,   152064, 0x4c9737ab
+0,         38,         38,        1,   152064, 0x0b07594c
+0,         40,         40,        1,   152064, 0xd2735925
+0,         42,         42,        1,   152064, 0x20cebfa9
+0,         44,         44,        1,   152064, 0xfd500471
+0,         46,         46,        1,   152064, 0x09ef53ff
+0,         48,         48,        1,   152064, 0xbb87b483