[Gretl-devel] MPI update

This is a follow-up to http://lists.wfu.edu/pipermail/gretl-devel/2014-March/004937.html There's an updated version of the preliminary documentation for gretl's MPI support at http://users.wfu.edu/cottrell/tmp/gretl-mpi.pdf The changes are not many or large: * $havempi replaced by $sysinfo.mpi * new option --local for mpi blocks * path to mpiexec now configurable via GUI * MPICC envvironment variable can be used when configuring an MPI-enabled build of gretl Allin