[qtmozembed] Send keyevent after each input commit 

This improves handling of sites like m.facebook.com and m.linkedin.com where button next to comment text field only listens to keyevents and ignores composition and input events. With this fix we send dummy keyevent after commit of pre-edit. In practice the button would change into active when user either 1) selects suggested works, commits with space or enter, or commits by tapping somewhere in the UI.

Google Chrome on Android uses similiar approach, but it sends dummy keyevents for each change of pre-edit in addition to commits.