_LT_AC_TAGCONFIG versus Cray sed

[Kevin Ryde]

On an sv1-cray-unicos10.0.0.X with the cvs libtool I noticed the
following error,

        configure: creating libtool
        sed: 1: "s/[-_ABCDEFGHIJKLMNOPQR ...": RE error: [ ] imbalance or 
syntax error
        appending configuration tag "CXX" to libtool

which I think might be from _LT_AC_TAGCONFIG,

        case `$echo "X$tagname" | $Xsed -e 
's/[[-_ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890,/]]//g'` 
in

There was a discussion not so long ago about using "/" in a character
range when it's also the delimiter, but I forget what the theory was.