``mk_genfile_common.py`` and adapt ``mk_util.py`` and
``mk_consts_files.py`` to use the code at its new location. The
interface has been changed slightly so that
``mk_z3consts_py_internal()`` now returns the path to the generated
file. The motivation behind this is so that clients of the function
know the path to the generated file.
Whilst I'm here also reindent ``mk_consts_files.py`` and move some of
its code into ``mk_genfile_common.py`` so it can be shared.
Also update Z3_GENERATED_FILE_EXTRA_DEPENDENCIES in the CMake build
so it knows about ``mk_genfile_common.py``.
The purpose of this change is to have Python code common to the Python
and CMake build systems separate from Python code that is only used for
the Python build system.
function ``mk_z3consts_py_internal()`` which called by a new
``mk_consts_files.py`` script. This will script will allow the const
declarations for the different Z3 language bindings to be generated.
Right now only support for python is implemented but more can be added
in the future.
