#change UBT will check for API version of all UnrealHeaderTool binaries to detect partial syncs
#change Added BuildHostPlatform class for runtime platform abstraction
[CL 2245408 by Robert Manuszewski in Main branch]
Previously PushDir_NoExceptions would change the current working directory, and push the NEW working directory onto the stack,
thereby losing the ability to pop the final directory and return to the original working directory before anything was pushed.
This old behavior contradicted the method's comment, which reads "Pushes the current working directory onto a stack and sets CWD to a new value."
[CL 2236817 by Richard Fawcett in Main branch]
- Fixes correct (normalized) filename not being used in FileExists().
- Removes unused variables (safe fix).
This is a subset of changes (compiler warning fixes needed for Linux editor) from pull request 185 by sbc100, 3dluvr, wshearn, abarbu et al (#ue4linux community): https://github.com/EpicGames/UnrealEngine/pull/185
#codereview Gil.Gribb, Robert.Manuszewski, Daniel.Lamb
[CL 2085591 by Dmitry Rekman in Main branch]
- Project rules will now be stored in EngineSavedFolder when running non-installed UAT, otherwise in Temp/UAT/EscapedRoot folder
- Added CommandUtils.EscapePath utility function
- Moved DeleteDirectoryContents function from LocalBuildEnvironment to CommandUtils
- Added code to clean rules folder up on startup.
#codereview gil.gribb
[CL 2044393 by Robert Manuszewski in Main branch]
