cleaned up function interface to avoid referencing the file system in the worker functions.
replaced StringTable's operators with functions.. The main reason is that these are far easier to look up when browsing the source.
This also fixes a premature translation in SBARINFO that was done in the parsing stage, not the printing stage.
The STARTUP0 check is not only redundant but also was wrong. It already gets checked and validated in the asset loading loop, and this up-front check did not handle placement as a graphic.
There seems to be a bug in the backend, but I have no idea what's wrong.
Clearing the start screen with a ClearRect call renders the 2D drawer in an unstable state. So for now, clear the screen by rendering a texture, but with light color black, which produces the same effect without later breaking stuff.
* for Strife the game palette must be loaded before the start screen.
* increase update frequency of start screen to roughly 35 fps
* fixed Strife's laser sprite names.
* do not show the native progress bar if a graphical start screen is used.
