[App] Add cache: -> \Cache0 symlink

I think this should be safe to do, seems games will only make use of either cache:, or cache0: & cache1:, not both kinds, so shouldn't be any risk of conflict.
cache: might only be used in older SDK cache code, at least so far I've only seen it used in the older Halo 3 Beta build.

src/xenia/app/xenia_main.cc

@@ -276,6 +276,7 @@ int xenia_main(const std::vector<std::wstring>& args) {
         XELOGE("Unable to register cache0 path");
       } else {
         emulator->file_system()->RegisterSymbolicLink("cache0:", "\\CACHE0");
+        emulator->file_system()->RegisterSymbolicLink("cache:", "\\CACHE0");
       }
     }