Add missing video_provider_cache.cpp.

Originally committed to SVN as r1948.

Add missing video_provider_cache.cpp.
39d0e31f · Amar Takhar · f2ca0c4f · 39d0e31f
--- a/aegisub/Makefile.am
+++ b/aegisub/Makefile.am
@@ -272,6 +272,7 @@ aegisub_SOURCES = \
 	video_frame.cpp \
 	video_provider.cpp \
 	video_provider_dummy.cpp \
+	video_provider_cache.cpp \
 	video_slider.cpp \
 	visual_feature.cpp \
 	visual_tool.cpp \