Use getch in game::death_screen instead of get_input

This follows the dialog that appears ("Press Spacebar to Quit").
astyle game::list_factions
use redraw variable to redraw the fractions dialog when the selection has changed.
Use input_context in game::list_factions instead of get_direction
Use input_context in game::list_missions
astyle game::msg_buffer
Use input_context instead of get_input in game::msg_buffer
Fix some warning about signed/unsigned values

Also fix the indentation in list_factions
Remove the InputEvent enum and the two functions that still use it.

Those two functions and the enum are not used anywhere else. Finally.