Bug in mp_get_r1
Apparently there is a small bug in this function of UtilXlib:
https://gitlab.com/QEF/q-e/blob/master/UtilXlib/mp.f90#L768
msglen
should be 1 but is 0 when MPI_RECV is called.
I'm still working on the unit testing framework for UtilXlib so I if it's not a problem I'd prefer to send the fix with a merge request (to avoid merge conflicts) when I'm done with the tests.