Fix a bug with addons installing:

A directory was created, with the addons name, in lowercase, whereas it tried to instal it in the addons name, in standard case (e.g. python vs Python).
So, it worked on Windows and Mac OS X, since they aren't case sensitive, but we had a segfault on Linux

git-svn-id: svn+ssh://svn.code.sf.net/p/supertuxkart/code/main/trunk@7266 178a84e3-b1eb-0310-8ba1-8eac791a3b58

src/addons/addons_manager.cpp

@@ -176,7 +176,7 @@ void AddonsManager::install(const Addon &addon)
 
     //extract the zip in the addons folder called like the addons name    
     std::string dest_file = file_manager->getAddonsDir() + "/"
-                          + addon.getType()+ "s/" + addon.getName() + "/" ;
+                          + addon.getType()+ "s/" + id + "/" ;
     std::string base_name = StringUtils::getBasename(addon.getZipFileName());
     std::string from      = file_manager->getAddonsFile(base_name);
     std::string to        = dest_file;