inputmethod: toggle the inputmethod if we get second show request

This is in a way working around bad protocol, input-method-unstable-v1
and also input-method-unstable-v2 does not have a way for input-method
to mark itself as "deactivated". This can happen when e.g. user closes
the virtual keyboard using swiping down or "close keyboard" button in
keyboard.

When this happens, the state between compositor, text_input and
input_method gets out of sync, compositor does not know that input
method got deactivated and hence it will continue sending various events
to it. The quick way around it is to change focus, which makes
compositor send deactivate request to input-method, that puts compositor
and input-method in sync again.

This patch aims to solve this by tracking the last state of input
method, If we know that input method is active and text input sends us
the show event, we toggle the input-method.

I will re-iterate that this is in no way proper solution, ideally
input-method-unstable-v3 or input-method-unstable-v2 even (since it is
not upstream anyway) gains the new request which essentially allows
input-method to sync enabled/disabled state with compositor.


(cherry picked from commit 892b8cf6)