Until now, only the event (press/release) for which a mapping was
present got eaten, and the other was passed to the client. From this
commit, a press mapping eats both events and a release mapping eats
nothing (and a press+release combo eats both).
This fixes behavior of some clients that do not make a difference
between press and release (e.g. Firefox with a fullscreen video
exiting fullscreen even on an Esc release event).
I have encountered a crash (failing assert) if a view specified a fixed
size less than this minimum, and according to ifreund this behavior was
planned to be removed, anyway.
