emulation: Don't report shift-left-button release
emulation: Don't report shift-left-button release

In case selection is deferred until the threshold is exceeded, we still need
to consume the event so that we don't report a button release event to the app.

https://bugzilla.gnome.org/show_bug.cgi?id=683729

pjm0616/vte,asivokon/vte-fx,jessevdk/vte,thestinger/vte-ng,saitoha/vte-sixel,rvu95/vte,rvu95/vte,asivokon/vte-fx,jessevdk/vte,flaxandteal/gasket-vte,rvu95/vte,jessevdk/vte,pjm0616/vte,flaxandteal/gasket-vte,saitoha/vte-sixel,flaxandteal/gasket-vte,asivokon/vte-fx,pjm0616/vte,flaxandteal/gasket-vte,asivokon/vte-fx,jessevdk/vte,saitoha/vte-sixel,rvu95/vte,thestinger/vte-ng,thestinger/vte-ng