Fix ffmpeg_mptr::seek_to() for Win32. Make error messages more informative.
Don't forget to change numeric locale when loading settings
Fix stability problems introduced by migration of layer parameters to ValueBase type.

When layer recieves or outputs the parameter values we need to create an independent copy of ValueBase object.
That way we avoid memory problems and unauthorized changes for parameter.
Fix headers. Cleanup.
Switch to 0.64.1-RC2
Update translations