* switching to recursive mutexes for now; easier to implement
* need to read user input from the window manager; hidden windows are
drawn when reading input from there
* note: occasional dead lock between PTY and ncurses mutex
* fixed type in class `SingleUserInput`
* using `get_wch()` now and mapping most of the function keys documented
in `vterm_keycodes.h` (not num keypad)
* there are still a lot of mappings from ncurses missing (in conjunction
with modifier keys, related issue #11)
* using mutex to make sure writing to terminal client is serialized
Christian Burger