quote.c: ensure the same quoting across platforms.

We read a byte from "char *" and compared it with ' ' to decide
if it needs quoting to protect textual output.  With a platform
where char is unsigned char that would give different result.
Signed-off-by: NJunio C Hamano <junkio@cox.net>

quote.c

@@ -209,7 +209,7 @@ static int quote_c_style_counted(const char *name, int namelen,
 		if (!ch)
 			break;
 		if ((ch < ' ') || (ch == '"') || (ch == '\\') ||
-		    (ch == 0177)) {
+		    (ch >= 0177)) {
 			needquote = 1;
 			switch (ch) {
 			case '\a': EMITQ(); ch = 'a'; break;