Support for inline doctype rules plus newlines.

This adds support for lexing/parsing XML documents that use an IO as input _and_
contain doctype rules with newlines in them.

This fixes #63.

lib/oga/xml/parser.y

@@ -86,12 +86,17 @@ rule
       }
 
     # <!DOCTYPE html [ ... ]>
-    | T_DOCTYPE_START T_DOCTYPE_NAME T_DOCTYPE_INLINE T_DOCTYPE_END
+    | T_DOCTYPE_START T_DOCTYPE_NAME doctype_inline T_DOCTYPE_END
       {
         on_doctype(:name => val[1], :inline_rules => val[2])
       }
     ;
 
+  doctype_inline
+    : T_DOCTYPE_INLINE                { val[0] }
+    | doctype_inline T_DOCTYPE_INLINE { val[0] + val[1] }
+    ;
+
   # CDATA tags
 
   cdata