Fixed the case insenstive search under unices

src/osgDB/FileUtils.cpp

@@ -441,11 +441,13 @@ std::string osgDB::findFileInDirectory(const std::string& fileName,const std::st
             // See if we're already at the top level of the filesystem
             if ((parentPath.empty()) && (!lastElement.empty()))
             {
+                std::string directoryStringToUse = (realDirName[0]=='/' || realDirName[0]=='\\') ? std::string("/") : std::string(".");
+
                 // Search for the first path element (ignoring case) in
                 // the top-level directory
-                realDirName = findFileInDirectory(lastElement, "/",
+                realDirName = findFileInDirectory(lastElement, directoryStringToUse,
                                                   CASE_INSENSITIVE);
-      
+
                 dc = osgDB::getDirectoryContents(realDirName);
                 needFollowingBackslash = true;
                 needDirectoryName = true;