Add ability to select numeric base when displaying symbol values in readelf.

Add ability to select numeric base when displaying symbol values in readelf.

	PR 27672
	* readelf.c (sym_base): New variable.
	(enum print_mode): Add more modes.
	(print_vma): Add suport for new modes.
	(options): Add sym-base.
	(usage): Add sym-base.
	(parse_args): Add support for --sym-base.
	(print_dynamic_symbol_size): New function.
	(print_dynamic_symbol): Use new function.
	* doc/binutils.texi: Document the new feature.
	* NEWS: Mention the new feature.