Add functions from <libgen.h>

Add memrchr.c

git-svn-id: svn://kolibrios.org@7949 a494cfbc-eb01-0410-851d-a64ba20cac60

programs/develop/ktcc/trunk/libc/string/memrchr.c

@@ -0,0 +1,12 @@
+/* memrchr.c from musl
+ */
+
+#include <string.h>
+
+void *memrchr(const void *m, int c, size_t n)
+{
+	const unsigned char *s = m;
+	c = (unsigned char)c;
+	while (n--) if (s[n]==c) return (void *)(s+n);
+	return 0;
+}