Fixing Boost build with Clang 3.4

This applies the following Boost patches that have already been applied
upstream:

https://github.com/boostorg/atomic/commit/6bb71fdd8f7cc346d90fb14beb38b7297fc1ffd9.patch
https://github.com/boostorg/atomic/commit/e4bde20f2eec0a51be14533871d2123bd2ab9cf3.patch

These patches will be in Boost 1.56 but until then we need to make the local
changes.

Fixes #864
Resolving a minor lint error