Add missing include for stdlib.h.

The test math/test-nan-overflow uses malloc without including
stdlib.h. On -Os builds for i486 the header inclusion order
is altered enough that the test fails to build because of the
warning which is turned into an error.

The obvious fix is to include stdlib.h since malloc is being
used directly.

ChangeLog

@@ -1,3 +1,7 @@
+2016-10-28  Carlos O'Donell  <carlos@redhat.com>
+
+	* math/test-nan-overflow.c: Include stdlib.h for malloc.
+
 2016-10-28  H.J. Lu  <hongjiu.lu@intel.com>
 
 	[BZ #20019]

math/test-nan-overflow.c

@@ -20,6 +20,7 @@
 #include <stdio.h>
 #include <string.h>
 #include <sys/resource.h>
+#include <stdlib.h>
 
 #define STACK_LIM 1048576
 #define STRING_SIZE (2 * STACK_LIM)