Add support for C++

[ysc3839]

Previous pull request #118 was closed accidentally.

Add preprocessor definitions (macros) with git info to C++ and resource compiler.

Using this way is because there's no easy way to inject global variables into a source file. Users are required to include a header in order to use generated git info.
And C++ has multiple char types, for example "str" is char[] and L"str" wchar_t[]. And there's no easy way to do a compile-time conversion.
But with macros, we can just use a macro like #define WSTRIFY(s) L##s to make it become wchar_t[]
Also the resource compiler doesn't support global variables, but macros are supported.

Currently there's a issue that Visual Studio says identifier "GIT_*" is undefined. A solution is to write a stub header file that checks existence these macros and define them if not exist.

Another option is to generate a header file with preprocessor definitions, and let user manually include it. Which one is better?

May closes #67, but I'm not familiar with managed C++.

[kzu]

Closing for now from lack of movement and since there seem to be a couple issues mentioned that still don't work (from my basic understanding of the PR description). Lack of support for managed C++ also seems to be a drawback.