Prepare for the change of the NAMD reduction interface

[HanatoK]

David Clark from NVIDIA is working on extending the GPU-resident code to multiple nodes. He has proposed to refactor and unify the reductions of energies and virials in NAMD, as the old NodeReduction class only works for the single-node code path. I have proposed to change NAMD_VERSION_NUMBER to 34471682L after David Clark's MR (see https://gitlab.com/tcbgUIUC/namd/-/commit/e81f36cc733d884f2aa2699449a61fa4c68483dc on a hackathon branch). This PR changes the colvarproxy_namd.* to check the NAMD_VERSION_NUMBER to determine whether NodeReduction should be used.