change bjam to b2 in developer docs

git-svn-id: http://svn.boost.org/svn/boost/trunk@83579 b8fc166d-592f-0410-95f2-cb63ce0dd405
Add redirect for gil.io documentation.

git-svn-id: http://svn.boost.org/svn/boost/trunk@83581 b8fc166d-592f-0410-95f2-cb63ce0dd405