skins2: For playlist controls, keys to be forwarded to vlc core
skins2: For playlist controls, keys to be forwarded to vlc core

the playlist control entirely redefines key processing (arrows, enter, ...).
Yet, for keys not processed, forwarding them to vlc core is desirable.
For instance, that enables n(ext) and p(revious) when focus is on the playlist,
which is something users can expect to be working.

vlc-mirror/vlc,jomanmuk/vlc-2.2,krichter722/vlc,vlc-mirror/vlc-2.1,vlc-mirror/vlc,vlc-mirror/vlc,krichter722/vlc,vlc-mirror/vlc,xkfz007/vlc,jomanmuk/vlc-2.1,krichter722/vlc,shyamalschandra/vlc,xkfz007/vlc,jomanmuk/vlc-2.1,xkfz007/vlc,shyamalschandra/vlc,jomanmuk/vlc-2.1,shyamalschandra/vlc,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,shyamalschandra/vlc,vlc-mirror/vlc,xkfz007/vlc,xkfz007/vlc,jomanmuk/vlc-2.2,shyamalschandra/vlc,jomanmuk/vlc-2.1,jomanmuk/vlc-2.2,krichter722/vlc,jomanmuk/vlc-2.2,xkfz007/vlc,xkfz007/vlc,jomanmuk/vlc-2.1,vlc-mirror/vlc,krichter722/vlc,krichter722/vlc,vlc-mirror/vlc-2.1,jomanmuk/vlc-2.1,shyamalschandra/vlc,krichter722/vlc,shyamalschandra/vlc,jomanmuk/vlc-2.2,vlc-mirror/vlc-2.1,vlc-mirror/vlc-2.1,vlc-mirror/vlc-2.1,vlc-mirror/vlc,jomanmuk/vlc-2.1,vlc-mirror/vlc-2.1,vlc-mirror/vlc-2.1