Addition of a build system generator

[elfring]

I suggest to reuse a higher level build system so that powerful checks for software features will become easier.

• CMake
• Autotools

[ocornut]

Not seeing the point. Would go against the simplicity and dropability of the library. As we go on the code can be fixed to increase portability without relying on extra tools. Onward it would be beneficial to have a more thorough way of testing compilation on different compilers/architectures.

[elfring]

I imagine that development efforts become bigger without the support of a dedicated build system. I would appreciate if existing portability checks can be reused here.