`make check' with --enable-shared

[Alexandre Oliva]

When the srcware tree is configured with --enable-shared, the `expect'
program won't run properly.  Jim Wilson found out gdb has a local hack
to set LD_LIBRARY_PATH, but, AFAIK, no other project has been hacked
similarly.

Here's a simple patch that renders that gdb hack obsolete, and
arranges for all packages to automatically benefit from it.  I'm not
reverting the gdb hack, though.  I'll leave that to the gdb hackers
:-)

Here's the patch I'm checking in, approved by Jim Wilson: