Small issue in m4/lx_find_mpi.m4: Echo vs echo

[cschwan]

First, thanks a lot for this file! I found it when I saw your answer on stackoverflow.com and use it now for one of my projects.

I found a tiny error with the last echo in file m4/lx_find_mpi.m4 at line 200, which is mistakingly spelled with a captial letter: Echo.