Correct cdtest g++ version test

Fixes declaration conflict with built-in strncpy.

	* testsuite/ld-cdtest/cdtest-foo.cc: Test for __GNUG__ >= 2.

ld/ChangeLog

@@ -1,3 +1,7 @@
+2016-12-03  Alan Modra  <amodra@gmail.com>
+
+	* testsuite/ld-cdtest/cdtest-foo.cc: Test for __GNUG__ >= 2.
+
 2016-12-03  Alan Modra  <amodra@gmail.com>
 
 	* ldexp.c (try_copy_symbol_type): Remove unnecessary check.

ld/testsuite/ld-cdtest/cdtest-foo.cc

@@ -5,7 +5,7 @@
 // We don't use header files, since we only want to see, whether the
 // compiler is installed properly.
 //
-#if (__GNUG__ == 2)
+#if __GNUG__ >= 2
 typedef __SIZE_TYPE__ size_t;
 #else
 typedef unsigned int size_t;