This moves the version numbers into an isolated configured header so
that not all of CMake needs to rebuild when the version changes.

Previously we had spaces, dashes and/or the word 'patch' randomly chosen
before the patch number.  Now we always report version numbers in the
traditional format "<major>.<minor>.<patch>[-rc<rc>]".

We still use odd minor numbers for development versions.  Now we also
use the CCYYMMDD date as the patch number of development versions, thus
allowing tests for exact CMake versions.