fixes for rpmbuild

fixes for rpmbuild

This patch fixes some makefile/specfile issues when running
rpmbuild with the distributed lxc specfile:

- fixes usage of installation directories for config files,
  rootfs, templates and lxc-init so that they're calculated
  at make time instead of configure time. Thanks to this,
  all installed items go under $RPM_BUILD_ROOT when running
  rpmbuild
- introduce --disable-rpath option to configure to avoid
  check-rpaths errors when building non-root.
- introduce a lxc-libs package in the default spec file
  to allow concurrent installation of 32 bit and 64 bit
  libraries.

v2: - fix circular reference in lxc.pc
    - ship lxc.pc with lxc-devel

Signed-off-by: Greg Kurz <gkurz@fr.ibm.com>
Signed-off-by: Daniel Lezcano <dlezcano@fr.ibm.com>