stream_filter/httplive.c: Rewrite relativeURL (fix #4268)
stream_filter/httplive.c: Rewrite relativeURL (fix #4268)

The relativeURL function missed various checks to determine the correct
location for the next download. Checking not only the meta playlist locations,
but also the HLS playlist locations itself should fix #4268.

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