Primitive Types: change Slice to RandomAccessSlice at append

Related: attaswift#9

SipHash/Primitive Types.swift

@@ -12,7 +12,7 @@ extension SipHasher {
     /// Add the contents of `slice` to this hash.
     ///
     /// - Requires: `finalize()` hasn't been called on this instance yet.
-    public mutating func append(_ slice: Slice<UnsafeRawBufferPointer>) {
+    public mutating func append(_ slice: RandomAccessSlice<UnsafeRawBufferPointer>) {
         self.append(UnsafeRawBufferPointer(rebasing: slice))
     }