Add missing function in 20_util/exchange/1.cc.

When this test is compiled at -O0, the compiler does not remove the
address comparison. This causes a link failure, since the body of f()
is missing.

	* testsuite/20_util/exchange/1.cc: Add missing function
	bodies.

From-SVN: r203629

libstdc++-v3/ChangeLog

+2013-10-15  Diego Novillo  <dnovillo@google.com>
+
+	* testsuite/20_util/exchange/1.cc: Add missing function
+	bodies.
+
 2013-10-15  Tim Shen  <timshen91@gmail.com>
 
 	PR libstdc++/58737

libstdc++-v3/testsuite/20_util/exchange/1.cc

@@ -55,6 +55,10 @@ test02()
   VERIFY( old.value == 1 );
 }
 
+int f(int) { return 0; }
+
+double f(double) { return 0; }
+
 // Deduce type of overloaded function
 void
 test03()
@@ -62,8 +66,6 @@ test03()
   bool test __attribute__((unused)) = true;
 
   int (*fp)(int);
-  int f(int);
-  double f(double);
   std::exchange(fp, &f);
   VERIFY( fp != nullptr );
 }