[boost] Removing support for old compilers

Hi Stephen As part of your initiative of removing support for old compilers, are you building somewhere a change log in the form of either a list of compiler deficiencies or compiler versions no longer supported? I understand this should be inserted in a prominent place on the Boost 1.56 release notes and can serve as a reference for lib maintainers reviewing your patches (tracking changesets is harder and commit messages are not always completely illuminating). Thank you, Joaquín M López Muñoz Telefónica Digital