Add intrinsics support (#121)

* Initial intrinsics support

* Update tests to work with the new Vector128 type and intrinsics

* Drop SSE4.1 requirement

* Fix copy-paste mistake

ChocolArm64/AOptimizations.cs

@@ -1,6 +1,12 @@
+using System.Runtime.Intrinsics.X86;
+
 public static class AOptimizations
 {
     public static bool DisableMemoryChecks = false;
 
     public static bool GenerateCallStack = true;
+
+    public static bool UseSse2IfAvailable = true;
+
+    internal static bool UseSse2 = UseSse2IfAvailable && Sse2.IsSupported;
 }