1. check if plug-ins path is a directory 2. wrap dynamic loading into try/catch to play nicer on win32  
1. check if plug-ins path is a directory
2. wrap dynamic loading into try/catch to play nicer on win32
 


git-svn-id: 5adfda8227e14e59fd47d5bd9925a30df16fed74@472 d397654b-2ff0-0310-9e29-ba003691a0f9

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