Replace hidden with versioned in elf_link_hash_entry

Replace hidden with versioned in elf_link_hash_entry

This patch replaces the "hidden" field with the "versioned" field in
elf_link_hash_entry so that we can avoid calling strchr and strrchr if
the symbol is unversioned.

	* elf-bfd.h (elf_symbol_version): New enum.
	(elf_link_hash_entry): Replace hidden with versioned.
	* elflink.c (_bfd_elf_merge_symbol): Don't look for symbol
	version if the symbol is unversioned.  Initialize versioned.
	(_bfd_elf_add_default_symbol): Don't look for symbol version
	if the symbol is unversioned or hidden.  Initialize versioned.
	(elf_collect_hash_codes): Don't look for symbol version if the
	symbol is unversioned.
	(elf_collect_gnu_hash_codes): Likewise.
	(bfd_elf_gc_mark_dynamic_ref_symbol): Likewise.
	(_bfd_elf_link_hash_copy_indirect): Check versioned instead of
	hidden.
	(elf_link_output_extsym): Likewise.