* read.h (enum linkonce_type): Define.

	* read.h (enum linkonce_type): Define.
	(s_linkonce): Declare.
	* read.c (potable): Add "linkonce".
	(s_linkonce): New function.
	* subsegs.h (segment_info_type): Add linkonce field to
	MANY_SEGMENTS && ! BFD_ASSEMBLER section.
	* config/obj-coff.h (obj_handle_link_once): Define if TE_PE.
	(obj_coff_pe_handle_link_once): Declare if TE_PE.
	* config/obj-coff.c: If TE_PE and not BFD_ASSEMBLER, #include
	"coff/pe.h".
	(obj_coff_pe_handle_link_once): New function, defined if TE_PE.
	(c_section_symbol): If TE_PE, set the x_comdat field in the aux
	entry based on the linkonce field in segment_info.
	* doc/as.texinfo: Document .linkonce.