GPVAL_TERM_WINDOWID under wxt (and qt)

[Petr M. <mi...@ph...>]

The GPVAL_TERM_WINDOWID works now OK under X11 terminal. It would be nice to 
add this functionality under wx terminal (and qt) as well.

Under wxt, I think it is just needed to update
	gp_exec_event(GE_plotdone, 0, 0, 0, 0, windowid);
with the windoid being the actual x11 window id, not a "local" number.

Could somebody provide a patch?

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PM