Merge "libc: fix memchr implementation" into integration

lib/libc/memchr.c

@@ -9,10 +9,10 @@
 
 void *memchr(const void *src, int c, size_t len)
 {
-	const char *s = src;
+	const unsigned char *s = src;
 
 	while (len--) {
-		if (*s == c)
+		if (*s == (unsigned char)c)
 			return (void *) s;
 		s++;
 	}