rtlib/gfxlib2: Use CINT() macro for rounding to (32-bit) int
(like FB's cint(), except it rounds up fractions of 0.5,
i.e. away from 0, instead of to even.)
Draw: ensure clean diagonal lines

Remove dependence on imprecise floating-point constants (e.g. PI, SQRT_2) by using degrees and handling diagonal drawing with a boolean value.

Also call dedicated line-drawing code, rather than drawing and incrementing pixel-by-pixel.

Line-drawing code pulled out of fb_GfxLine() into separate fb_GfxDrawLine().

Also remove +0.5,0.5 on "Mx,y", which brought about the conditions for the wobbling, and was causing #478
Fix wstring-indexing in integer var initializers

Reported by Mysoft on IRC.
Merge remote-tracking branch 'origin/master'

Conflicts:
	changelog.txt