.gdbinit: fix print_pathobj

$str is not C string but RString.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@60835 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

.gdbinit

@@ -1110,7 +1110,7 @@ define print_pathobj
     else
       set $str = ((struct RArray*)($arg0))->as.heap.ptr[0]
     end
-      printf "%s", $str
+    print_string $str
   end
 end