* Add partial range subscripts to _UnmanagedOpaqueString
* Use SipHash13+_NormalizedCodeUnitIterator for String hashes on all platforms
* Remove unecessary collation algorithm shims
* Pass the buffer to the SipHasher for ASCII
* Hash the ascii parts of UTF16 strings the same way we hash pure ascii strings
* De-dupe some code that can be shared between _UnmanagedOpaqueString and _UnmanagedString<UInt16>
* ASCII strings now hash consistently for in hashASCII() and hashUTF16()
* Fix zalgo comparison regression
* Use hasher
* Fix crash when appending to an empty _FixedArray
* Compact ASCII characters into a single UInt64 for hashing
* String: Switch to _hash(into:)-based hashing
This should speed up String hashing quite a bit, as doing it through hashValue involves two rounds of SipHash nested in each other.
* Remove obsolete workaround for ARC traffic
* Ditch _FixedArray<UInt8> in favor of _UIntBuffer<UInt64, UInt8>
* Bad rebase remnants
* Fix failing benchmarks
* michael's feedback
* clarify the comment about nul-terminated string hashes
* Make Range conditionally a Collection
* Convert ClosedRange to conditionally a collection
* De-gyb Range/ClosedRange, refactoring some methods.
* Remove use of Countable{Closed}Range from stdlib
* Remove Countable use from Foundation
* Fix test errors and warnings resulting from Range/CountableRange collapse
* fix prespecialize test for new mangling
* Update CoreAudio use of CountableRange
* Update SwiftSyntax use of CountableRange
* Restore ClosedRange.Index: Hashable conformance
* Move fixed typechecker slowness test for array-of-ranges from slow to fast, yay
* Apply Doug's patch to loosen test to just check for error
Include the initial implementation of _StringGuts, a 2-word
replacement for _LegacyStringCore. 64-bit Darwin supported, 32-bit and
Linux support in subsequent commits.
