allow <CTRL/C> to be typed; aborts last typed char

 * CTRL/C will be a command so it is important to be able to type it directly
 * aborting character processing is important because it allows aborting infinite loops
 * since the loop interruption currently relies on SIGINT handling, there is only limited
   support for XCurses and GTK - CTRL/C has to be typed in the terminal window.
   later support for input queue polling might be added
updated copyright (2012-2013)
support only Scinterm >= v1.1 (contains SCI_COLOR_PAIR macro and indirectly fixes PDCurses support)
added TODO list

also updated AUTHORS
added patch enabling TECO-style (^X) control code echoing in Scintilla

in the future, I might submit a more elaborate Scintilla patch for configuring
the control code strings.