Return syntax error message when issuing invalid instance specific control command in VLM. ("control test thisisaninstanceid play" is valid, "control test thisisaninstanceid asdqsd" isn't).

A bit of cleanup in simple prefs

instead of aborting

* wxwidgets: revert go-where-you-click slider changes from [15391] and [15393] as it wasn't optimal (more accurate at the middle and not so much towards the beginning or end) and this also prevented proper slider select and drag usage.

  to avoid crashes in the messaging system (global data has no libvlc pointer)
- Rename ROOT to GLOBAL to avoid confusion (the root is LIBVLC, not GLOBAL)

- Remove some cruft

(And go fix your libc if this does not work for you.)

   leak in the TS mux which is triggered when the input PCR packets
   disappear from the stream without disappearing from the PMT (happens
   on the satellite when the video suddenly gets scrambled). Insert it in
   the sout pipeline : --sout="#autodel:std{...}".

retry on failure to connect to rc-unix socket. Patch by Greg Farrell (greg  a  lincor.com), submitted by Dermot McGahon (dermot  a  dspsrv.com)

(could be improved, but basically works)