* xcofflink.c (XCOFF_DESCRIPTOR): Define.

	* xcofflink.c (XCOFF_DESCRIPTOR): Define.
	(struct xcoff_link_hash_table): Add descriptor_section and
	special_sections fields.
	(_bfd_xcoff_bfd_link_hash_table_create): Initialize new fields.
	(xcoff_link_add_symbols): Set linkage section alignment.  Create
	descriptor section.  Check for magic symbol names (_text, etc.),
	and record them in special_sections if found.  Set
	XCOFF_DESCRIPTOR flag for a function descriptor, and set its
	descriptor field to point back to the function code symbol.
	(xcoff_sweep): Always mark the special descriptor_section.
	(bfd_xcoff_export_symbol): Check whether the symbol might be a
	function descriptor, and mark it if it is.
	(bfd_xcoff_size_dynamic_sections): Add new special_sections
	parameter, and fill it in.  Allocate space for the descriptor
	section.
	(xcoff_build_ldsyms): Set XCOFF_DEF_REGULAR flag when defining
	global linkage code.  If an undefined function descriptor is
	exported, arrange to define it.  Warn about any other undefined
	exported symbol.
	(_bfd_xcoff_bfd_final_link): Write out the descriptor section.
	(xcoff_write_global_symbol): Create a function descriptor when
	necessary.
	* bfd-in.h (bfd_xcoff_size_dynamic_sections): Update declaration.
	* bfd-in2.h: Rebuild.