readelf verdef and verneed

readelf verdef and verneed

readelf ought to notify when a symbol wrongly has both a version
definition and a needed version.  This patch does that, and removes
the heuristic that only defined symbols in SHT_NOBITS sections have
verneed entries.

	* readelf (process_version_sections): Check DT_VERNEED and
	DT_VERDEF for all symbols.  Report "*both*" should a symbol
	have both a verneed and verdef.
	(get_symbol_version_string): Reduce indentation by early
	exits.  Don't use SHT_NOBITS heuristic to detect case where a
	defined symbol has a verneed entry.