As suggested by Joshua, this commit adds the 2-clause BSD license as a
comment block to the top of every source file.
For the first pass, I've just added myself for simplicity. I encourage
everyone to add themselves as copyright holders of any file they've
added or modified in some significant way. If I've added myself in
error somewhere, feel free to replace it with the appropriate copyright
holder instead.
Going forward, all new source files should include a license header.
After I made stdio buffered, we were dropping anything unflushed on exit.
Since /bin/clear just prints out some escape sequences without a newline,
the entire buffer was being discarded.
Also add VirtualConsole::clear() that handles clearing of background VC's.
