scons: make sure to check for boost_python (closes #229), improve checking of boost version (closes #236), and fetch ABI version from mapnik/version (closes #72), as well as adding PathAccept for all PathVariables to account for various 64bit systems.
scons: make sure to check for boost_python (closes #229), improve checking of boost version (closes #236), and fetch ABI version from mapnik/version (closes #72), as well as adding PathAccept for all PathVariables to account for various 64bit systems.

git-svn-id: 5adfda8227e14e59fd47d5bd9925a30df16fed74@923 d397654b-2ff0-0310-9e29-ba003691a0f9

makinacorpus/mapnik2,craigds/mapnik2,makinacorpus/mapnik2,craigds/mapnik2,craigds/mapnik2,makinacorpus/mapnik2,makinacorpus/mapnik2,craigds/mapnik2