Increase the size of the die/warning buffer to avoid truncation

Long messages like those from lockfile.c when a lock can't be
obtained truncate with only 256 bytes in the message buffer.
Bump it to 1024 to give more space for these longer cases.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

usage.c

@@ -7,7 +7,7 @@
 
 static void report(const char *prefix, const char *err, va_list params)
 {
-	char msg[256];
+	char msg[1024];
 	vsnprintf(msg, sizeof(msg), err, params);
 	fprintf(stderr, "%s%s\n", prefix, msg);
 }