Mods to improve compatibility with IBM compilers

Small code and Makefile changes to improve compatability with the IBM XLF and XLC compilers.
For example, XLC does not like "//" style comments in .c files while XLF does not like comments
in preprocessor directives (e.g., "#include "size.h" ! comment") and is also picky about arguments
to intrinsic functions like min and max.

Changes to be committed:

  modified:   driver/petsc3.4/Makefile
  modified:   models/petsc3.4/mobi1.6/src/external_forcing_mobi.c
  modified:   models/petsc3.4/mobi1.6/src/npzd_src.F
  modified:   models/petsc3.4/npzddop/src/external_forcing_kiel_biogeochem.c
  modified:   models/petsc3.4/npzddop/src/insolation.F
  modified:   models/petsc3.4/ocmipabiotic/src/external_forcing_ocmip_abiotic_landatm.c