Added a generic atomic<> implementation based on the new __atomic intrinsics available in gcc 4.7 and clang 3.2. The new implementation adds support for 128-bit atomic. Other implementations updated to employ new macros in Boost.Config for defaulted and deleted functions (this is not complete yet). Fixed padding for the lock pool. Initializing constructor for atomic<> made explicit to avoid ambiguities of different overloads of operator=.

svn path=/trunk/boost/atomic/; revision=84800