Back porting native JSON support from SpiderMonkey 1.85 to SpiderMonkey 1.70 (github.com)

* What is "native JSON support"? - The "JSON" object. - "JSON.parse()" function which parse a JS object into JSON string. - "JSON.stringify()" function which generate a JS object from a JSON string.

* Why? - SpiderMonkey a widely used opensource JS engine. - But the later version since v1.70 requires MinGW to build on Windows platform. - v1.70 is the last version which is able to be compiled into a native Windows lib/dll, but it doesn't have native JSON support.

This project is to provide a native SpiderMonkey lib/dll on Windows with native JSON support.

* How to build? - Open Visual Studio Command Prompt - Debug build: nmake -f "js.mak" CFG="jsshell - Win32 Debug" - Release build: nmake -f "js.mak" CFG="jsshell - Win32 Release"