FEAT: added ATAN2 native support.
FIX: missing RPi compilation target in help page.
Merge pull request #895 from Oldes/atan2

FEAT: added ATAN2 native support.
FIX: uncommented the right docstring for the ROUND mezz function.
Merge remote-tracking branch 'origin/master' into master-oldes

Conflicts:
	boot.red
	runtime/macros.reds
	runtime/natives.reds