The MPP and MPPX builds of Molpro have been merged and the decision to
run in MPP or MPPX mode made a run-time option. To build parallel Molpro
-mpp flag to configure should be used; the
is no longer required or valid. When running parallel Molpro, the
--mpp option (default) can be used to specify MPP mode, and the
--mppx option for MPPX mode.