PR ld/12365

	PR ld/12365
include/
	* bfdlink.h (struct bfd_link_callbacks): Modify multiple_definition
	and multiple_common parameters to pass in a bfd_link_hash_entry
	pointer rather than name,bfd etc. found in the hash entry.
bfd/
	* elflink.c (_bfd_elf_merge_symbol): Update multiple_common calls.
	* linker.c (_bfd_generic_link_add_one_symbol): Likewise.  Call
	multiple_definition regardless of allow_multiple_definition.
	* simple.c (simple_dummy_multiple_definition): Update.
	* xcofflink.c (xcoff_link_add_symbols): Update multiple_definition
	calls.
ld/
	* ldmain.c (multiple_definition): Take a bfd_link_hash_entry
	pointer arg rather than "name", "obfd", "osec", "oval".  Add code
	removed from linker.c.  Hack around xcofflink.c oddity in
	passing NULL nbfd.
	(multiple_common): Similarly.
	* plugin.c (orig_allow_multiple_defs): Delete.
	(plugin_call_all_symbols_read): Don't twiddle allow_multiple_definition.
	(plugin_multiple_definition): Update.