pkt-line: rename packet_write() to packet_write_fmt()

packet_write() should be called packet_write_fmt() because it is a
printf-like function that takes a format string as first parameter.

packet_write_fmt() should be used for text strings only. Arbitrary
binary data should use a new packet_write() function that is introduced
in a subsequent patch.

Suggested-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Lars Schneider <larsxschneider@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

connect.c

@@ -730,7 +730,7 @@ struct child_process *git_connect(int fd[2], const char *url,
 		 * Note: Do not add any other headers here!  Doing so
 		 * will cause older git-daemon servers to crash.
 		 */
-		packet_write(fd[1],
+		packet_write_fmt(fd[1],
 			     "%s %s%chost=%s%c",
 			     prog, path, 0,
 			     target_host, 0);