Generate/update Fortran 77 interface files with make.

The code is quite complicated because of the following requirements and
limitations:

1. We keep the generated files in the develop branch and want to update them
   in the maintainer mode even if building out-of-source.

2. We have to support the distribution of the files over a VCS, which does not
   keep the timestamps, therefore, the files must not depend on anything in
   non-maintainer mode.

3. Files <prefix>.inc and <prefix>Fortran.c are generated with a single command
   and must be consistent, which makes the recovery in non-maintainer mode
   difficult. For example, we must not use <prefix>.inc from the source
   directory and <prefix>Fortran.c from the build directory. Also, the files
   must not be changed in the source directory in non-maintainer mode.

4. The console output of make_fint is very verbose and confusing for an
   unprepared user, therefore, we should call it in non-maintainer mode only
   when recovering.

In fact, we can have much more simple code if we fix #4 and stop distributing
the files because building make_fint does not require any extra tools or
libraries.