The problem here was that the world start position of the tool was being compared to a world-projected pixel position, which had vastly different depth values. This has been fixed by storing the start and end position in pixel space and using that for the distance calculation, rather than a world-space position. This would need re-thinking if we wanted the tool to work in perspective viewports, but that was a problem with the old code as well.
Also made the measurement display in more relevant units, rather than just showing raw uu.
This addresses TTP#344821 - CRITICAL: Regression: EDITOR: Ruler gives incorrect measurements.
[CL 2277554 by Andrew Rodham in Main branch]
#proj core
#branch UE4
#summary Rename Trunc, Round, Floor, Ceil to TruncToInt, RoundToInt, FloorToInt, CeilToInt. Added *ToFloat versions. Repeated for FGenericPlatformMath and all derived classes for all platforms wherever applicable. Corrected comment in Fractional and added Frac() which does HLSL-style fractional (x - floor(x)). Checked for compilation on all projects (with cooking levels wherever applicable). Didn't change Fractional to Frac, this will be done in second commit.
#codereview robert.manuszewski
[CL 2064306 by Mikolaj Sieluzycki in Main branch]
