Branch for adding initializer list support (only in the unreleased gcc 4.4 at the moment).

svn path=/branches/initializer-list/boost/signals.hpp; revision=48931
Initialise svnmerge.

svn path=/branches/initializer-list/boost/signal.hpp; revision=48951
Merge from trunk to make sure I don't accidentally merge the accidental initialize-list commit and rollback.

svn path=/branches/initializer-list/boost/last_value.hpp; revision=48952