Bump version after 4.6.4 release

Change-Id: Ied0463a471657e39cb6c4c41d6112f5778ef00d5
corrected potential nbnxn SIMD memory issue

A fixed size array on the stack was declared with one element
too few. Probably this never caused trouble with 64-bit builds,
but it might have caused trouble with 32-bit builds.

Change-Id: I4dad0a7a9e80f5d27ac6ee7e4383082db654481a
Enhanced warning message in case of unaccounted ions
Merge branch 'release-4-6' into comp_el_r46