[XA.Tools.Bytecode] Add Kotlin support to our binding process. (#505)

Context: #525

Various fixes and enhancements to allow better default Kotlin
libraries bindings:

  * Hide Kotlin-internal classes, constructors, and methods.

  * Hide implementation methods (`*-impl*`).

  * Rename extension method parameter like
    `$this$decodeBase64` to `obj`. 

  * Use Kotlin provided method parameter names instead of
    `p0`, `p1`, etc.

  * Rename any method with a `-<mangling>` to drop the invalid part,
    e.g. `add-H4uI21a` is bound as `add`.
    ("Name mangling" like this is how Kotlin ensures `add(UInt)` and
    `add(Int)` don't clash when compiled to [Java][1].)

Note that the final bullet point -- "removing" name mangling -- may
result in C# code which is either not valid or not entirely usable.
See Issue #525 for details.  This will be addressed "later".

[1]: https://kotlinlang.org/docs/reference/inline-classes.html#mangling

src/Xamarin.Android.Tools.Bytecode/ClassFile.cs

@@ -186,6 +186,8 @@ public bool IsStatic {
 		public bool IsEnum {
 			get {return (AccessFlags & ClassAccessFlags.Enum) != 0;}
 		}
+
+		public override string ToString () => ThisClass?.Name.Value;
 	}
 
 	[Flags]

src/Xamarin.Android.Tools.Bytecode/ClassPath.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
 using System.IO;
@@ -8,7 +8,6 @@
 using System.Xml.Linq;
 using System.Xml.XPath;
 using System.Text;
-using Xamarin.Android.Tools.Bytecode.Kotlin;
 
 namespace Xamarin.Android.Tools.Bytecode {