SvIV_nomg is available only for newer perls (>= 5.8.9)

For older perls, fallback to SvIV, like it was before commit
44f542394c0f86d6a4cbe6abd600d81a29b561ae.
wm-time.t: protect from GNOME shell slowness
inc VERSIONs
update Changes for Tk-804.031_503