#663 Add more hardware decoder options

[elvissteinjr]

mpv comes with a bunch of hardware decoding options, but the selection in SMPlayer is very limited.
Depending on the system and input it may be of advantage to be able to select from a wider selection.
Alternatively, a text field for custom input could be added.

As of now, mpv is ignoring any duplicate defintion of the hwdec argument, so adding one manually to the commandline does nothing.

[Ricardo Villalba]

I've just added the rest of options (svn r 8462).