PPTC & Pool Enhancements. (#1968)

* PPTC & Pool Enhancements.

* Avoid buffer allocations in CodeGenContext.GetCode(). Avoid stream allocations in PTC.PtcInfo.

Refactoring/nits.

* Use XXHash128, for Ptc.Load & Ptc.Save, x10 faster than Md5.

* Why not a nice Span.

* Added a simple PtcFormatter library for deserialization/serialization, which does not require reflection, in use at PtcJumpTable and PtcProfiler; improves maintainability and simplicity/readability of affected code.

* Nits.

* Revert #1987.

* Revert "Revert #1987."

This reverts commit 998be765cf.

ARMeilleure/CodeGen/X86/CodeGenerator.cs

@@ -190,6 +190,11 @@ namespace ARMeilleure.CodeGen.X86
 
                 byte[] code = context.GetCode();
 
+                if (ptcInfo != null)
+                {
+                    ptcInfo.Code = code;
+                }
+
                 Logger.EndPass(PassName.CodeGeneration);
 
                 return new CompiledFunction(code, unwindInfo);