fixes

suppress more system libraries in asan (triggered in ci)

…. not tested on web and android.

…the target buffer should be srgb, so writing without encoding will result in sth that is decoded 1 time too often.

the symbols look a bit wrong (probably their texture needs the srgba format).

…l you need an extension, which i didn't test). so imo the better option is to manually encode after we are done.

in theory we could do better by manually encoding in the g-buffer. however, the difference is hardly perceptible (i saw sth in the decoration buffer with the labels), and we risk other problems (sb. forgets it, bad filtering or blending).

fix handling of gamma encoding

…re from the marching, which is probably also incorrect)

fix atmosphere somewhat when zooming far out (there is still atmoshpe…