ecore_evas-x11: unset withdrawn state when window is mapped

ecore_evas-x11: unset withdrawn state when window is mapped

according to ICCCM 4.1.4:
Newly created top-level windows are in the Withdrawn state.
Once the window has been provided with suitable properties,
the client is free to change its state...
...
Only the client can effect a transition into or out of the Withdrawn state

given that no external force can (according to spec) transition a
window out of the withdrawn state, this must be done at a reasonable
point. mapping the window seems like a reasonable point to me.

fix T2745
ref 5954289c6ce1cd55ff212428291604b981438439

@fix