convert versions into a format more suitable for EUMM

Older EUMM versions complain about dotted decimal versions with v
prefixes.  Without the v prefix, they will at least pass the versions
through more properly to MYMETA and Makefile files, so other parts of
the toolchain can handle them.  Remove the v prefix for multi-dot
versions, and convert single dot versions to their numified form.

This is an attempt at fixing #171 and #293