failure with -gdwarf-4

pahole doesn't understand the new DWARF 4 .debug_types section.

I'm using the F15 GCC, but really any recent-enough GCC will do.
I compile this:

    struct s
    {
      int x;
      int y : 5;
      int z;
    };
    struct s i;

    int main()
    {
    }

Like so:

    gcc -gdwarf-4 -g -o d d.c

Running pahole gives an error:

    $ pahole --class_name=s ./d
    tag__recode_dwarf_type: couldn't find 0x1d type for 0x51 (variable)!

It would be nice to have support for this feature in dwarves, as
.debug_types can greatly reduce the size of the debuginfo in the final
executable.