ToJson still creates invalid Json when encoding +/- infinity and NaN

[thoj]

NeoLua Version: 1.3.14

Example to reproduce:

local f = { v = clr.System.Double.NaN };

print (table.ToJson(f))

I never got around to testing the fix. It apparently only was fixed for Lson and not Json.

https://github.com/neolithos/neolua/commit/7232cd3ceb647922f4d7bb4e445eb1b50dab8901

Realated issue: #135