protocol.h: move definition of DEFAULT_GIT_PORT from cache.h

Michael J Gruber noticed that connection via the git:// protocol no
longer worked after a recent header clean-up.  This was caused by
funny interaction of few gotchas.  First, a necessary definition

	#define DEFAULT_GIT_PORT 9418

was made invisible to a place where

	const char *port = STR(DEFAULT_GIT_PORT);

was expecting to turn the integer into "9418" with a clever STR()
macro, and ended up stringifying it to

	const char *port = "DEFAULT_GIT_PORT";

without giving any chance to compilers to notice such a mistake.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

daemon.c

@@ -4,6 +4,7 @@
 #include "config.h"
 #include "environment.h"
 #include "pkt-line.h"
+#include "protocol.h"
 #include "run-command.h"
 #include "setup.h"
 #include "strbuf.h"