* utils/split_file.py compatible Inputs/Template.swift.gyb
* Result scripts can be ran by %target-run-simple-swift, not GYB
* Renamed stdlib/Slice/*.swift.gyb to stdlib/Slice/*.swift
Removing the “checksAdded” parameter from collection unit tests and
simply sharing a global variable is a better way to go. We don't
use threads at that level, so there's no thread safety issue, and we
already committed to globals when we introduced the logging wrappers.