swift234

Merge remote-tracking branch 'apple/master'

# Conflicts:
#	stdlib/private/SwiftPrivate/ShardedAtomicCounter.swift
#	stdlib/public/core/ArrayCast.swift
#	stdlib/public/core/Collection.swift
#	stdlib/public/core/ContiguousArrayBuffer.swift
#	stdlib/public/core/StringBuffer.swift
#	stdlib/public/core/StringUnicodeScalarView.swift
#	test/1_stdlib/Builtins.swift
#	test/1_stdlib/Collection.swift
#	test/1_stdlib/ErrorType.swift
#	test/1_stdlib/ErrorTypeBridging.swift
#	test/1_stdlib/ExistentialCollection.swift
#	test/1_stdlib/Float.swift
#	test/1_stdlib/Map.swift
#	test/1_stdlib/Mirror.swift
#	test/1_stdlib/Optional.swift
#	test/DebugInfo/arg-debug_value.swift
#	test/DebugInfo/closure.swift
#	test/DebugInfo/for.swift
#	test/DebugInfo/return.swift
#	test/Interpreter/availability_weak_linking.swift
#	test/Interpreter/break_continue.swift
#	test/SILGen/sil_locations.swift
#	test/SILGen/statements.swift
#	test/SILGen/unreachable_code.swift
#	test/SILPasses/definite_init_diagnostics.swift
#	test/SILPasses/return.swift
#	test/SILPasses/switch.swift
#	test/SILPasses/unreachable_code.swift