[4.1, libstdc++] ld version detection

[Paolo Carlini]

Matthias Klose wrote:

>The following patch was applied on the trunk and the 4.2 branch, but
>skipped on the 4.1 branch. Needed to get the version extraction right
>with recent binutils from CVS.  Checked in as obvious.
>
Maybe obviously correct, but not obvious in the sense of obviously 
appropriate, wanted, approved, if you understand what I mean. Anyway, ok 
with me.

Paolo.