Fix tst-dlsym-error build

This patch fixes the new test tst-dlsym-error build on aarch64
(and possible other architectures as well) due missing strchrnul
definition.

	* elf/tst-dlsym-error.c: Include <string.h> for strchrnul.

ChangeLog

@@ -1,3 +1,7 @@
+2016-03-31  Adhemerval Zanella  <adhemerval.zanella@linaro.org>
+
+	* elf/tst-dlsym-error.c: Include <string.h> for strchrnul.
+
 2016-03-31  Florian Weimer  <fweimer@redhat.com>
 
 	[BZ #19509]

elf/tst-dlsym-error.c

@@ -20,6 +20,7 @@
 #include <gnu/lib-names.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 
 /* Used to disambiguate symbol names.  */
 static int counter;