Escape all messages in osc.lua, because other than the title they
weren't being escaped at all. If for example you did mpv foo.mp4
'{\fs50}bar.mp4' and script-message osc-playlist, it would just render
the second entry as bar.mp4 in big text.
The title was escaped partially, now the escaping is complete because:
- It escapes \. Backslashes at the end of the title are escaped instead
of being stripped, and \n, \N and \h are now printed verbatim. In
particular, "\\n" is no longer converted to space and is printed
verbatim instead which is more correct.
- Newlines ("\n", not the "\\n" escape sequence) are converted to spaces
instead of rendering them and messing up the text positioning within
the OSC.
- Spaces at the start are preserved.
Fixes#11209, fixes#11275.
Guido Cella
c84bb1ce67