binutils: introduce the infrastructure to support binutils alternatives

Rework binutils in order to provide soon binutils alternative.

Signed-off-by: Yann Diorcet <diorcet.yann@gmail.com>
[yann.morin.1998@free.fr: split up original patch for self-contained changes]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Message-Id: <d3d1d51f399e6d2c1163.1353320546@macbook-smorlat.local>
Patchwork-Id: 199971

 reporter_name="Ioannis E. Venetis"

 reporter_url="http://sourceware.org/ml/crossgcc/2011-05/msg00005.html"

 reporter_comment=""