Reinstating a heavily modified version of r10402. This is to do

Reinstating a heavily modified version of r10402.  This is to do
with #190429.

This patch (originally from Jakub Jelinek) makes the redir of strlen
in ld.so on amd64-linux ld.so mandatory, but only for glibc 2.10 and
above.  For glibc-2.2 (our earliest supported version) to glibc-2.9
it is still optional.

Also, makes more verbose, the message that is printed if a mandatory
ld.so redirection on Linux cannot be set up.

Is believed to fix #190429.

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@10689