infiniband: Adding support for almost all targets

To install the infiniband stuff we just need to add this line on the
targets that require IB support.

    install_ib_if_needed $ORIG $dir

This script is taking care of two variables.
- ENABLE_IB=y which enable the integrated IB support
- ENABLE_MELLANOX=y which uses Mellanox packages instead of integrated
  ones. Only works on Ubutu 12.04 for now but could be extended to
  other.

Thoses two variables are appended on the Makefile as shown in this
patch.

Users can use them like :
    make ceph ENABLE_IB=y ENABLE_MELLANOX=y DVER=IB DIST=precise

Enjoy,