Send those ctrl-alt key combos that QEMU doesn't treat specially to
the guest rather than ignoring them.

All the case where we do special handling of ctrl-alt-X exit the
event handling using a "return" statement, so we can simply allow
the rest to fall through into the normal key handling by deleting
the now-spurious "else".

We take the opportunity to clean up some oddly-formatted and
now rather uninformative comments by removing them.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>