merged from trunk

svn path=/branches/proto/v4/libs/rational/; revision=45289
merged from trunk

svn path=/branches/proto/v4/boost/rational.hpp; revision=45844
merged from trunk

svn path=/branches/proto/v4/boost/rational.hpp; revision=47983
merged from trunk

svn path=/branches/proto/v4/libs/rational/; revision=49607