Merge from trunk.

svn path=/branches/quickbook/backend/boost/tools/quickbook/; revision=38774
Merge from trunk.

svn path=/branches/quickbook/backend/boost/tools/quickbook/; revision=39329
Merge latest quickbook from trunk.

svn path=/branches/quickbook/backend/boost/tools/quickbook/; revision=40450
Add include-path (I) option so that one can refer to files to import or include outside of the usual quickbook tree without using absolute paths.

svn path=/branches/quickbook/backend/boost/tools/quickbook/; revision=40452
Commit old quickbook backend changes.

svn path=/branches/quickbook/backend/boost/tools/quickbook/; revision=59592