[Mono-dev] System.Json is ready to be replaced

[Atsushi Eno]

Hello,

As many of you guys already know, Microsoft did a huge ASP.NET source 
release at codeplex[*1]. Since this includes System.Json, I ported this 
to our class libs to replace existing stuff.

There are only a few concerns.

- There was some weird test that expects *invalid* JSON syntax.
   I'm totally inclined to kill it, but since this says as if
   .NET allowed such broken JSON (this actually fails with this
   Microsoft implementation), I'd wait for inputs regarding this one
   for a few days. Looks like it was from Miguel [*2]
- I haven't verified builds other than net_2_0, net_4_0 and net_4_5.
   I have excluded DLR stuff with NET_4_0 so this should build on
   other profiles though.
- The new dll is binary incompatible. I believe that in general
   Microsoft implementation makes more sense though (lots of explicit
   operators instead of implicit, Save() only on JsonValue, no
   TimeSpan support).

The new sources are in mcs/class/System.Json-new so the existing
System.Jsoncan be easily replaced with it.

[*1] http://aspnetwebstack.codeplex.com
[*2] 
https://github.com/mono/mono/blame/master/mcs/class/System.Json/Test/System.Json/JsonValueTest.cs

Atsushi Eno