lua_osd: add some parameters to the osd.message function to allow the user to set duration and position.

While the configure checks were platform-agnostic, the implementation
was Windows-specific. Worse, this code now conflicts with our Unicode
filesystem layer, which uses the same function names. In practice, this
code was never used.

On Windows, wcstombs() converts UTF-16 to ANSI, not to UTF-8.

They may be inconsistent on broken multi-processor hardware. But the
system tick count is causing worse problems with power saving features.

This reverts commit 4d636fa3.

This reverts commit a869d39d.

It isn't dangerous, helps people that use those features in playlists,
although those playlists are VLC-specific

(still default enabled, but now it's save to use the OS X defaults without bothering about it)

Up to now, notification of invalidated subareas was available for controls
but yet, the layout always ended up being totally rebuilt. For instance,
 a small animated image meant a total rebuild of everything. For simple skins,
 this could go unnoticed, but old computers had much difficulty with more
 complex skins (e.g wmp11), that were mostly busy rebuilding layouts
 over and over.

This patch ensures that only what needs to be rebuilt is rebuilt. Some skins
 like wmp11 on Linux do show dramatic improvement with this one patch.