[stdlib] Add 256 bits of extra state to Hasher

Author: lorentey

stdlib/public/core/SipHash.swift

@@ -28,6 +28,11 @@ internal struct _SipHashState {
   fileprivate var v1: UInt64 = 0x646f72616e646f6d
   fileprivate var v2: UInt64 = 0x6c7967656e657261
   fileprivate var v3: UInt64 = 0x7465646279746573
+  // The fields below are reserved for future use. They aren't currently used.
+  fileprivate var v4: UInt64 = 0
+  fileprivate var v5: UInt64 = 0
+  fileprivate var v6: UInt64 = 0
+  fileprivate var v7: UInt64 = 0
 
   @inline(__always)
   fileprivate init(rawSeed: (UInt64, UInt64)) {

test/api-digester/Outputs/stability-stdlib-abi.swift.expected

@@ -52,6 +52,10 @@ Var _CocoaDictionary.Index._offset is added to a non-resilient type
 Var _CocoaDictionary.Index._storage in a non-resilient type changes position from 1 to 0
 Var _CocoaSet.Index._offset is added to a non-resilient type
 Var _CocoaSet.Index._storage in a non-resilient type changes position from 1 to 0
+Var _SipHashState.v4 is added to a non-resilient type
+Var _SipHashState.v5 is added to a non-resilient type
+Var _SipHashState.v6 is added to a non-resilient type
+Var _SipHashState.v7 is added to a non-resilient type
 
 /* Decl Attribute changes */