No code in MESA makes use of this

None of this code is used in the other parts of MESA.

It is only used for non-sdk builds, and other required libraries (such
as HDF5) are not included for non-sdk builds as well. Furthermore, this
prevents the vendored version from being out of date with the SDK
version.

This commit introduces a new build system (still based on make files).
Reasons for replacing the previous build system were:

- the previous build system had a lot of duplication between the
  modules, both in terms of make files and shell scripts.
- parallelisation was limited. The new build system parallelises better
  within a module, and between modules.
- build scripts and output from the build ended up in the same folder.
  With the new system, all build output files are stored in the folder
  ``build`` in the repository root, making cleaning build files
  equivalent to deleting this folder

For the details of the implementation, see the newly added documentation
(Developing -> Build system).

Some further notable changes:

- makedepf90 has been replaced by a perl script that scans the fortran
  source files. This allows for better flexibility in construction the
  make files.
- Currently, `pymesa` does not work with the new build system, as the
  new system does not provide a way to build shared libraries for every
  module.
- Dependencies are being discovered using pkg-config. This change
  makes it easier to build MESA without the SDK, as linux distributions
  typically ship with pkg-config files.

This commit adds the necessary pkg-config files until the SDK ships
them.