add back ltdl global advise

ltdl-mapnik.diff

diff --git a/src/datasource_cache.cpp b/src/datasource_cache.cpp
index dd1721c..c129276 100644
--- a/src/datasource_cache.cpp
+++ b/src/datasource_cache.cpp
@@ -160,11 +160,35 @@ void datasource_cache::register_datasources(const std::string& str)
             {
                 try 
                 {
-#if (BOOST_FILESYSTEM_VERSION == 3)   
-                    lt_dlhandle module = lt_dlopen(itr->path().string().c_str());
+
+                    lt_dlerror();
+
+                    lt_dlhandle module = 0;
+                    lt_dladvise advise;
+                    int ret;
+
+                    ret = lt_dlinit();
+                    if (ret != 0) {
+                        std::clog << "Datasource loader: could not intialize dynamic loading: " << lt_dlerror() << "\n";
+                    }
+
+                    ret = lt_dladvise_init(&advise);
+                    if (ret != 0) {
+                        std::clog << "Datasource loader: could not intialize dynamic loading: " << lt_dlerror() << "\n";
+                    }
+
+                    ret = lt_dladvise_global(&advise);
+                    if (ret != 0) {
+                        std::clog << "Datasource loader: could not intialize dynamic loading of global symbols: " << lt_dlerror() << "\n";
+                    }
+#if (BOOST_FILESYSTEM_VERSION == 3)
+                    module = lt_dlopenadvise (itr->path().string().c_str(), advise);
 #else // v2
-                    lt_dlhandle module = lt_dlopen(itr->string().c_str());
-#endif
+                    module = lt_dlopenadvise (itr->string().c_str(), advise);
+#endif 
+
+                    lt_dladvise_destroy(&advise);
+
                     if (module)
                     {
                         // http://www.mr-edd.co.uk/blog/supressing_gcc_warnings