Do not set x-display-name until X connection is established.

Do not set x-display-name until X connection is established.
This is needed to prevent from weird situation described at
<http://lists.gnu.org/archive/html/emacs-devel/2013-04/msg00212.html>.
* frame.el (make-frame): Set x-display-name after call to
window system initialization function, not before.
* term/x-win.el (x-initialize-window-system): Add optional
display argument and use it.
* term/w32-win.el (w32-initialize-window-system):
* term/ns-win.el (ns-initialize-window-system):
* term/pc-win.el (msdos-initialize-window-system):
Add compatible optional display argument.