scons: improve handling of optional plugin paths by only adding paths if a plugin will be built, prepending plugin paths to ensure linking against requested libs, and maintaining sorting of internal includes and libs given new plugin prepend behavior (addresses #250)
scons: improve handling of optional plugin paths by only adding paths if a plugin will be built, prepending plugin paths to ensure linking against requested libs, and maintaining sorting of internal includes and libs given new plugin prepend behavior (addresses #250)

git-svn-id: 5adfda8227e14e59fd47d5bd9925a30df16fed74@968 d397654b-2ff0-0310-9e29-ba003691a0f9

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