The alt buffer is now cleared immediated after activating the normal buffer and
is filled when switching to it. The tests were failing because the alt buffer
wasn't being cleared properly with the previous solution.
This brings in proper support to resize both buffers (#510) and fixes an
exception that was caused by wrongfully not clearing the normal buffer when
resizing while the alt buffer is active.
There was an obscure bug in this that could have caused some great confusion
later on; When switching to the alt buffer, a hard terminal reset was performed
which tried to retain the buffers. However, because buffers was initialized in
the Terminal constructor to a new BufferSet, the Terminal.buffer convenience
pointer was pointing at a stale alt buffer which was the one actually being
used, not Terminal.buffers.alt.
Fixes#842Fixes#510
Daniel Imms
Paris Kasidiaris
Oleksandr Andriienko