Enable building primme with CMake (also under MSVC)

[juanjosegarciaripoll]

• Add CMakeLists.txt files for building the library and examples
• Enable building with and without Fortran compilers
• Enable compiling the library using Microsoft's C++ compiler.

Using MSVC++ is required because MSVC (the C compiler) does not support C99 complex types and, more important, generic mathematical functions. I made minimal changes. Fortunately primme is very well architected in this sense.

With these changes, I can now create a recipe for building primme into vcpkg and use it from arbitrary C++ projects. See https://github.com/juanjosegarciaripoll/vcpkg-ports and the subdirectory ports/primme for how simple it is to add it to this distribution.