[0.4.0-Alpha] Ansi redisplay parts of old buffer on new screen

[M-griffin]

When testing screens in Oblivion/2 XRM I noticed the Sysop screen was drawing then re-displaying part of the screen. When testing again 3.x version it didn't have this problem. Check that the buffer is clearing properly on clear screen codes, and also do a comparison with the 3.x version.

Some code was rolled back and still needs to be re-implemented in 4.x