Ignoring namespaces for issue#17

Just ignoring namespace and backslahes in class names(wanted sgrep to work for files with namespaces), doesn't work correctly at all(i mean pretty-printer and others will just lose  namespace keyword).

Also couldn`t figure out how to concat namespace names.

```ocaml
fully_qualified_class_name:
+  | backslashed_name { Name $1}

+backslashed_name: 
+  | ident { $1 }
+  | T_BACKSLASH ident { $2 }
+  | backslashed_name T_BACKSLASH ident { $3 }
```
should be something like this 
```ocaml
+  | backslashed_name T_BACKSLASH ident { Ast.rewrap_str 
(Ast.info_to_str $1 ^ Ast.info_to_str $2 ^ Ast.info_to_str $3) 
$1  }
```
But my ocaml-fu is not good enough to code it correctly.