CL# 2698724:
UHT speed improvements:
Code is now generated with tabs, rather than going through a separate Tabify step.
Some expensive temporaries created during iteration and during iteration have been removed.
FFunctionData::FunctionDataMap now uses unique ownership instead of shared ownership.
TCString::Spc (and the new TCString::Tab) now uses a compile-time array instead of one generated at runtime with a static.
TSet::Compact no longer rehashes if no compaction was performed.
TArray assignment no longer reallocs to the same capacity.
[CL 2698780 by Steve Robb in Main branch]