This is a lot easier to manage than having them in the code.
For now it piggybacks on the map hack feature, later this should use the same scripted approach as GZDoom.
This is by no means a permanent solution but having it buys some time to find something more universal that won't affect performance too badly and investigate the need for a more robust solution.
The idea here is to define pairs of walls where when the first element of the pair is seen, it will treat the second one as view blocking.
This is used as the two offending windows (sectors 151 and 152) to cope with the lack of a height sensitive clipper.
* Using the Doom-style dome here because it looks better.
* this necessitated changes to the backend to allow both types of sky domes at the same time
* do not clamp panning fields for cloudy sky with the new renderer because this makes the texture jump.
The duplicate 'currentSprite' variable prevented it from doing anything.
Also cleaned up the interface a bit to avoid using a global variable for parameter passing.
Fixes#279
This is needed to extend a few fields that are too narrow - e.g. the texture offset fields have no room for interpolating scrolling textures.
Blood not done yet, will also need to be changed to get rid of the limits.
