Fix two more cases where a libc_hidden_proto was added to string.h while

no libc_hidden_def exists for the function.

libc/string/memccpy.c

@@ -18,3 +18,4 @@ void *memccpy(void * __restrict s1, const void * __restrict s2, int c, size_t n)
 
 	return (n == (size_t) -1) ? NULL : r1;
 }
+libc_hidden_def(memccpy)

libc/string/strlcat.c

@@ -44,3 +44,4 @@ size_t strlcat(register char *__restrict dst,
 
 	return len;
 }
+libc_hidden_def(strlcat)