fix cmake regex for finding MPI version
fix cmake regex for finding MPI version

cmake regex is greedy, which means that the old regex
MPI_VERSION.*([0-9]+)
would only put the last digit of the version into the group \1 because
.* consumes the others. Fix this.

naliboff/dealii,EGP-CIG-REU/dealii,kalj/dealii,naliboff/dealii,danshapero/dealii,sairajat/dealii,kalj/dealii,EGP-CIG-REU/dealii,sairajat/dealii,danshapero/dealii,danshapero/dealii,sairajat/dealii,danshapero/dealii,danshapero/dealii,kalj/dealii,EGP-CIG-REU/dealii,EGP-CIG-REU/dealii,sairajat/dealii,naliboff/dealii,sairajat/dealii,EGP-CIG-REU/dealii,kalj/dealii,naliboff/dealii,danshapero/dealii,sairajat/dealii,danshapero/dealii,naliboff/dealii,kalj/dealii,naliboff/dealii,sairajat/dealii,kalj/dealii,kalj/dealii,EGP-CIG-REU/dealii,EGP-CIG-REU/dealii,naliboff/dealii