This adds Bracketed Paste support for terminals that have mouse
support and support it. The bracketing events are EventPaste,
with methods to note Start() or End() of the paste. Content
comes in as normal rune events. Programs must opt-in to this by
calling screen.EnablePaste().
* Make keyNames variable public
This map of variables might be useful to applications wanting to convert text to keys, e.g. for key bindings.
* Document KeyNames variable
fixes#38 Broke wide characters in last update
fixes#39 Clean up logic for encodings, enhance fallback options
fixes#36 Support more mouse buttons on Windows.