mingw: give waitpid the correct signature

POSIX says that last parameter to waitpid should be 'int',
so let's make it so.

Signed-off-by: Erik Faye-Lund <kusmabite@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

compat/mingw.c

@@ -1705,7 +1705,7 @@ char *getpass(const char *prompt)
 	return strbuf_detach(&buf, NULL);
 }
 
-pid_t waitpid(pid_t pid, int *status, unsigned options)
+pid_t waitpid(pid_t pid, int *status, int options)
 {
 	HANDLE h = OpenProcess(SYNCHRONIZE | PROCESS_QUERY_INFORMATION,
 	    FALSE, pid);