Warzone 2100 Graphic Mods tools

Bugfix atmos.c asAtmosParts exceeding array bounds, add error checking and also change the way the loop runs.

Bugfix: Fixed segfault relating to ticket number 6

Final change to skybox code.

Change to code to enable day/night

adding new sky textures and mod a building texture.

Don't draw clouds twice
Also work with hours, not seconds.

Untested changes to skybox to make them alternate between night and day depending on the hour.

tweak pie_InitSkybox() so page numbers are not hard-coded.
adds a new parameter clamp_or_repeat.

making the boot warzone blueish

adding new day sky textures background and sun.