BUGFIX missing files, FindMPI improved, Clang compatibility
- BUGFIX: fixed missing source files, that was broken by v2.1.0.21
- check and set flag
-Wnoimplicit-function-declarations
as Clang errors otherwise, and GCC emits lots of warnings otherwise - improved FindMPI with our own written from scratch--works better on MacOS and CentOS in particular and doesn't bother with ancient/obscure MPI implementations