CPLSpawn() on Windows: quote arguments with spaces in them (#5469)

git-svn-id: https://svn.osgeo.org/gdal/branches/1.11@27330 f0d54148-0727-0410-94bb-9a71ac55c965
PDF: fix compilation problem with Podofo on Windows (patch by keosak, #5469)

git-svn-id: https://svn.osgeo.org/gdal/branches/1.11@27331 f0d54148-0727-0410-94bb-9a71ac55c965