666405f: Simulator: improve simulation of transflective screens
This patch simulates the three possible states of a transflective LCD: backlight on (bright screen as usual), backlight off (dimmed screen) and LCD off (black screen). Makes use of already defined 'BACKLIGHT_OFF_ALPHA'.
2876859: Fix lcd not waking up when backlight is always off
This patch is relevant for targets with a transflective display. If the backlight was set to "always off" (e.g. to use the lcd in a pure passive way), and the sleep timer ran off, the LCD would stay disabled and didn't wake up when a button is pressed.