There's no painless way to do this, but it needs to be done --

the only reason any of the Windows code was in CPP files was
because the MS compiler doesn't support C99.  Switch to using
MinGW, and that problem goes away, so we can rename the files back.

client/Makefile.mingw

@@ -0,0 +1,11 @@
+CC=c:\mingw\bin\gcc
+
+LIBS   = -lgdi32 -lsetupapi
+
+all: proxmark3
+
+proxmark3: prox.c wingui.c command.c
+	$(CC) $(CFLAGS) $(DEFINES) -o prox.exe prox.c wingui.c command.c $(LIBS)
+
+clean:
+	del prox.exe