WIP: Assdraw

Include assdraw in aegisub, like in windows builds. Focus on the Linux/BSD build for the moment because it's where I can test

assdraw/Makefile

@@ -47,4 +47,4 @@ assdraw_SOURCES += \
 	$(d)resource.h
 
 
-assdraw_OBJ := $(assdraw_SOURCES:%.cpp/%.o)
+assdraw_OBJ := $(assdraw_SOURCES:.cpp=.o)