new branch to fix documentation

svn path=/sandbox-branches/birbacher/fix_documentation/boost/mpl/; revision=60575
merged changes from previous incarnation of this branch
svn merge -r56197:56494 https://svn.boost.org/svn/boost/sandbox-branches/birbacher/fix_documentation@56494 .

svn path=/sandbox-branches/birbacher/fix_documentation/libs/mpl/; revision=60577