Tidy:
* eliminate curses from Progress Bar
* move colour definitions to color.h
* tidy naming of color functions
* move KeyEvent out of mutt_curses.h
Refactor:
* SET_COLOR() to mutt_curses_set_color()
* NORMAL_COLOR() to mutt_curses_set_color()
* ATTR_SET() to mutt_curses_set_attr()
* curs_set() to mutt_curses_set_cursor()
* beep() to mutt_beep()
* addch() to mutt_window_addch()
* addnstr() to mutt_window_addnstr()
* addstr() to mutt_window_addstr()
* clrtobot() to mutt_window_clrtobot()
* move() to mutt_window_move_abs()
* printw() to mutt_window_printf()
* mutt_window_mvaddstr()
* clearok() to mutt_window_clear_screen()
* mutt_window_getxy() to mutt_window_get_coords()