Bug#961183: metis: providing a 64-bit build

[Drew Parsons]

Package: metis
Followup-For: Bug #961183

64-bit integers are now available for several libraries.

64-bit PETSc is able to use 64-bit SuperLU-Dist, which we don't
currently have.

64-bit SuperLU-Dist requires 64-bit metis.

In principle 64-bit metis is simple to configure: set IDXTYPEWIDTH to
64 in metis.h.

The challenge that we need to address is the location of metis.h.
Currently it's located in /usr/include/metis.h (for the standard 32-bit build)

To distinguish between standard and 64-bit builds, we'd probably want to place
the 64-bit header in /usr/include/metis64/metis.h

-I/usr/include/metis64 can then be used by client applications. The
remaining challenge is that /usr/include/metis.h might be found
instead of /usr/include/metis64/metis.h, since -I/usr/include will
also often be used in build scripts.

I think the best solution is to "break" the builds of client
applications by moving the standard header from /usr/include/metis.h
to /usr/include/metis/metis.h.  Then client applications will need to
be updated to add -I/usr/include/metis when using the standard build.