Fix bogus assertions in buffer.hxx
Standard terminal height is 24, not 25.
Add some convenience methods to Buffer.
Fixed bug where DECALN (Alignment Test) wasn't filling the screen.
Clamp to the margin in moveCursor
Fix bug: consider origin mode in VPA
Fixed bug ED0 and ED1 need to erase part of the current line too.
Fixed bug: squash 0 param for CSI sequences where it doesn't make sense
Clear the buffer for mode 1048 (alt screen)