Fortran codegen: Allow collecting profile information

@cory

@inducer Should I be using the system clock like the basic function you wrote for the test, or could I make use of, say, MPI_WTIME() as a timing function? There are already MPI_WTIME calls in the PlasComCM RHS that I'm putting into the Leap code and I'm not super clear on what to do about that.

It looks like plascom is already littered with calls to mpi_wtime, in which case using it is almost certainly the right thing.