tilegx: fix strstr to build and link better

The two_way_short_needle() routine included from str-two-way.h
is not used, so mark it so to avoid compiler warnings.

Calling strnlen() breaks linknamespace tests, so change it
to __strnlen().

ChangeLog

@@ -1,3 +1,8 @@
+2014-12-19  Chris Metcalf  <cmetcalf@ezchip.com>
+
+	* sysdeps/tile/tilegx/strstr.c (STRSTR): Call __strnlen, not
+	strnlen.
+
 2014-12-19  Ondřej Bílka  <neleai@seznam.cz>
 
 	* string/strncat.c (STRNCAT): Simplify implementation.

sysdeps/tile/tilegx/strstr.c

@@ -27,6 +27,7 @@
   (!memchr ((h) + (h_l), '\0', (j) + (n_l) - (h_l))	\
    && ((h_l) = (j) + (n_l)))
 #include "str-two-way.h"
+typeof(two_way_short_needle) two_way_short_needle __attribute__((unused));
 
 #undef strstr
 
@@ -238,7 +239,7 @@ STRSTR (const char *haystack_start, const char *needle_start)
     }
 
   /* Fail if NEEDLE is longer than HAYSTACK.  */
-  if (strnlen (haystack, needle_len) < needle_len)
+  if (__strnlen (haystack, needle_len) < needle_len)
     return NULL;
 
   /* Perform the search.  Abstract memory is considered to be an array