complibs: introduce generic multi-complibs infrastructure

Use the same method as companion tools for providing generic and
extendable companion libs.

Signed-off-by: Yann Diorcet <diorcet.yann@gmail.com>
Message-Id: <515c5c4635d99ebe4877.1353074410@macbook-smorlat.local>
Patchwork-Id: 199613

 #!/bin/sh

 set -e

 printf "Running autoconf...\n"

 autoconf -Wall --force

 printf "Done. You may now run:\n    ./configure\n"