Add c++14 sized deallocation operator

When compiling with -std=c++14 (the default for gcc 6.0+), the sized
deallocation operator must be defined to prevent undefined symbols when
linking.

winsup/cygwin/ChangeLog:
cxx.cc (operator delete(void *p, size_t)): Define.

Signed-off-by: Peter Foley <pefoley2@pefoley.com>

winsup/cygwin/cxx.cc

@@ -29,6 +29,11 @@ operator delete (void *p)
 {
   free (p);
 }
+void
+operator delete (void *p, size_t)
+{
+  ::operator delete(p);
+}
 
 void *
 operator new[] (std::size_t s)