CMake Build(issue #82)

[thebusytypist]

This pull request is for CMake build system support in RapidJSON. (issue #82)

It includes build scripts for examples, unittests, and a CMake module of RapidJSON.

Usage:

1. Run CMake client, then select the source path of RapidJSON and a build path(I suggest to use out-of-source build).
2. Configure and set some variables.
   For some version of Visual C++ on Windows, you may need to check gtest_force_shared_crt to ensure projects are linked to same type of CRT(multi-threaded dynamic).
3. Generate

Differences from current build system(premake):

• Code Generation Settings
  In premake build scripts, project test and project example have inconsistent code generation settings. In project test SSE4.2(-msse4.2) is enabled only for gmake configuration.While in project example, SSE2(flags { "Optimize", "EnableSSE2" }) is enabled for release configuration.

  Currently I leave the SSE optimization settings unset for both project unittest and project example.

  This does not affect the intrinsic sets you use(which is controlled by CMake variable RapidJSON_SIMD_OPTIMIZATION).

• Working Directory
  For Visual C++ you should set working directory manually because CMake cannot set it in an official documented way.

Please delay merging of this pull request. I have to test this on Xcode on a Mac OS X machine.

[miloyip]

Currently thirdparty/gtest is a Git submodule, is it possible to not adding gtest files in this pull request?

[pah]

Please use RAPIDJSON_BIGENDIAN and RAPIDJSON_LITTLEENDIAN instead of hard-coding 0 and 1.