Modernize Meson script

[denizzzka]

• Removes project_version and Co - Meson suggests different way to establish version compliance

• Removes install stuff - we don't need install this small source library (we do not need to be able to install every package from code.dlang.org in a row)

• Removes the meaningless division of deps variables to "source" or not

• Removes pkgconfig stuff (why and whom was need this?)

• Removes unnecessary for now build_machine.system() branch for MacOS

[denizzzka]

How to test:

# cmd:                     similar to:
$ meson setup builddir/     # mkdir builddir && cmake
$ cd builddir/
$ ninja -j1 test            # make -j1 test