mozilla: rework events

The mozilla webplugin events do not support arguments and expose all events available in libvlc. Most
of these events are not usefull for the webplugins and not being able to pass arguments is another limiting
issue. This patch addresses both problems at the same time.

The mozilla webplugin limits supports to the libvlc_MediaPlayer* events just like the ActiveX webplugin does.
These events are usefull in the context of a webplugin.

Ommit the 'libvlc_' prefix from the libvlc_MediaPlayer* events to obtain the events name that must be
used from JavaScript to listen on the event. Example:

- libvlc_MediaPlayerOpening becomes 'MediaPlayerOpening'
- libvlc_MediaPlayerNothingSpecial becoms 'MediaPlayerNothingSpecial'

Signed-off-by: Jean-Paul Saman <jean-paul.saman@m2x.nl>

Conflicts:

	projects/mozilla/vlcplugin.cpp
	projects/mozilla/vlcplugin.h