Replace/remove mentions of 320x200 resolution

[ivan-mogilko]

There are still few places in the manual where the command description mentions 320x200 resolution (or 320 width or 200 height) as something default or even maximum. In some cases it refers to the legacy 320x200 coordinate mode which has been deprecated over a decade ago.

Good example is these parts of the Engine plugin API:

https://github.com/adventuregamestudio/ags-manual/wiki/EnginePluginRun-timeAPI#iagsengineroomtoviewport

Converts the room co-ordinates (x, y) into current viewport co-ordinates. The input co-ordinates are room co-ordinates using the 320x200-style scheme that the text script uses and that object and character co-ordinates are stored as.

https://github.com/adventuregamestudio/ags-manual/wiki/EnginePluginRun-timeAPI#iagsenginegetwalkbehindbaseline

Returns the baseline for walk-behind area number area. This is always in character-resolution, i.e. the maximum value is 200 in all resolutions.

These should be removed or replaced with something more appropriate. I think searching for numbers "320", "200", "640", "400" may lead to these cases.