qt4: sout-widget changes to check mux
qt4: sout-widget changes to check mux

Doesn't allow mp4-muxer on other than file-output (doesn't check rtp atm).
Also tries to be littlebit clever and cleanup sout-mrl.

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