Partial revert of b14fc9d3d97811

Partial revert of b14fc9d3d97811

It turns out that there is just too much code which
rewuires writing to vp->vp_strvalue.  The regex comparisons,
xlat expansions, etc.  all require the ability to write
strings to integer-type attributes.

We'll see if there's a better way to fix this in the future.