From Farshid Lashkari, "A while back the behaviour of extension alias' was modified so that

the user can override existing alias'. The change allowed for circular
references, so the createLibraryNameForExtension would get caught in
an endless loop. The following fix will catch circular references."

src/osgDB/Registry.cpp

@@ -469,7 +469,7 @@ std::string Registry::createLibraryNameForExtension(const std::string& ext)
 {
 
     ExtensionAliasMap::iterator itr=_extAliasMap.find(ext);
-    if (itr!=_extAliasMap.end()) return createLibraryNameForExtension(itr->second);
+    if (itr!=_extAliasMap.end() && ext != itr->second) return createLibraryNameForExtension(itr->second);
 
 #ifdef OSG_JAVA_BUILD
     static std::string prepend = "java";