Use a proper file extension for C++

These don't exist on Linux, but they are a fun fiction.

Makefile

@@ -3,11 +3,11 @@ all: capture playback
 bin:
 	mkdir -p bin
 
-capture: bin capture.c
+capture: bin capture.cpp
 	g++ capture.c -o bin/capture
 
 clean:
 	rm -Rf bin
 
-playback: bin playback.c
+playback: bin playback.cpp
 	g++ playback.c -o bin/playback