Accept partial matches with -p <module name> (aka --module ...)

Accept partial matches with -p <module name> (aka --module ...)
Old behavior is still available by prefixing the module name with an
equal sign. For example "vlc -p ts --advanced" returns help on the mux_ts,
vod_rtsp, ts and dvb (aka atsc) modules while "vlc -p '=ts' --advanced"
returns help on the mux_ts (aka ts) and ts modules.