Add option to display hints in Dragon's Lair

[madebr]

This pr adds a hint mode to Dragon's Lair, enablable through the draw_hints cvar. It displays arrows or a sword if an action is available. Its color means dead (red) or alive (green).

I've drawn the sprites myself using PiskelApp, so they aren't top notch, but okay'ish :).

Other patches:

• I initially created BMP's with 24 bit depth, for which the error "Incomplete or corrupt .BMP file" was shown. Fix the error message by testing for bit depth first.
• The pixels of the bmp need to be byteswapped. I noticed this because red in the bmp was always black.
• Remove a duplicate action in the lua file

Screenshots: