replace Clamp() define with native clamp() function

replace Tan() define with native tan() function

replace roundNearest() define with native round(x, 1) function

replace CEILING(x, 1) use with simpler Ceiling() define, in 515 all Ceiling() use can be replaced by native ceiling()

replace FLOOR(x, 1) use with simpler Floor() define, in 515 all Floor() use can be replaced by native floor()

pulls out of projectile code and changed to a more robust version, copied from TGMC:
https://github.com/tgstation/TerraGov-Marine-Corps/blob/2da5c237640d73e3e66ad79e34861e9682f4609c/code/__DEFINES/maths.dm#L87-L90

replace n_ceil() use with Ceiling() define