This patch adds the ability to enable "input history" on a textbox,
allowing to navigate between the history with the arrow keys.
Also removes a custom TextBox subclass from HackStudio that added
the exact same hooks, and moves it to use the now standard ones.
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.
