lt_ld_extra computation via ld.so.conf is broken

[Tim Van Holder]

On GNU/Linux, the list of paths searched by the dynamic linker is
computed from the contents of ld.so.conf, using:

... | $SED -e '...;s/[:,\t]/ /g;...'

However, GNU sed (at least version 3.02, which is the most recent
version that is officially available for my system (RH8)) does not
support \t as an escape sequence.
As such I ended up with
"...:/op:/local-libs/:/usr/lib/q:-3.0.5/lib:..." instead of
"...:/opt/local-libs/:/usr/lib/qt-3.0.5/lib:...".  Using an actual TAB
character instead in the sed command  works just fine.

Seems to be present in both HEAD and 1.5.16.