Fix for issue #912 - missing catacurse functions

- Adds mvgetch, combination of move + getch
- Adds getnstr.
  Reads a given maximum number of characters into a string.
  Can either show or hide the input.
  Only supports basic editing (backspace).
- Slightly modified wish.cpp to accommodate for the modified echo functionality
  and to limit the maximum of given items at a time to 9999.