* cygheap.h (cygheap_fdmanip::release): Simplify.

* dtable.cc (dtable::release): Make void again.  Skip not_open check since it
is guaranteed to be open.  Don't bother deleting here since actual deletion
will be handled in cygheap_fdget::~cygheap_fdget.
* dtable.h (dtable::release): Make void again.
* syscalls.cc (dup2): Bump fhandler use count on successful dup.

winsup/cygwin/cygheap.h

@@ -407,12 +407,7 @@ public:
 	delete fh;
       }
   }
-  void release ()
-  {
-    fh = cygheap->fdtab[fd];
-    if (cygheap->fdtab.release (fd))
-      fh = NULL;
-  }
+  void release () { cygheap->fdtab.release (fd); }
 };
 
 class cygheap_fdenum : public cygheap_fdmanip