PR28459, readelf issues bogus warning

PR28459, readelf issues bogus warning

I'd missed the fact that the .debug_rnglists dump doesn't exactly
display the contents of the section.  Instead readelf rummages through
.debug_info looking for DW_AT_ranges entries, then displays the
entries in .debug_rnglists pointed at, sorted.  A simpler dump of the
actual section contents might be more useful and robust, but it was
likely done that way to detect overlap and holes.

Anyway, the headers in .debug_rnglists besides the first are ignored,
and limiting to the unit length of the first header fails if there is
more than one unit.

	PR 28459
	* dwarf.c (display_debug_ranges): Don't constrain data to length
	in header.