ENH: explictly set scotch INTSIZE. Tag scotch libs with -intNN ending

- Use WM_LABEL_SIZE to explicitly define INTSIZE32 or INTSIZE64, which
  ensures that SCOTCH_Num appears as (int32_t | int64_t) and avoids
  any ambiguity that a plain 'int' may have.

- Provide library symlinks to the respective label-size.
  Eg,  libscotch.so -> libscotch-int32.so

  This provides a unique library linkage name that avoids ambiguity
  with system-installed libraries.

- Use IDXSIZE64 (memory addressing width Fortran)

NOTE
  Unfortunately -DINT32 seems to fail if openmpi was built without Fortran!
  The MPI_INT32_T is interpreted as MPI_INTEGER4 which does not exist
  - needs more investigation

ENH: scotch - document Makefile.inc by copying into the source directory

ENH: update kahip build to use cmake for newer versions