* moved the sprite renaming out of the file system entirely into a caller-provided callback.
* renamed several functions to closer match the terms of a file system.
* moved the VM interface out of the implementation.
This is to keep as much higher level logic out of these as possible. The presentation of the data should be a concern of the file system, not the data containers.
This is not useful by itself but can be used for adding new features later, e.g. mod-wide compatibility settings or file specific lump replacement or injection.
With localization for non-Latin languages on the support list the multibyte API doesn't cut it anymore. It neither can handle system text output outside the local code page nor can an ANSI window receive text input outside its own code page.
Similar problems exist for file names. With the multibyte API it is impossible to handle any file containing characters outside the active local code page.
So as of now, everything that may pass along some Unicode text will use the Unicode API with some text conversion functions. The only places where calls to the multibyte API were left are those where known string literals are passed or where the information is not used for anything but comparing it to other return values from the same API.
