Remove link_info.pic

Remove link_info.pic

Adding type_pie to output_type allows us to remove link_info.pic and
with some reordering of the enum, produces better code.

include/
	* bfdlink.h (enum output_type): Delete type_executable, add type_pde
	and type_pie.  Reorder.
	(struct bfd_link_info): Delete pic field.
	(bfd_link_executable, bfd_link_pde, bfd_link_pie, bfd_link_pic): Adjust.
ld/
	* emultempl/aix.em: Don't set link_info.pic.
	* emultempl/pe.em: Likewise.
	* emultempl/pep.em: Likewise.
	* emultempl/sunos.em: Likewise.
	* lexsup.c (parse_args): Likewise.  Set type_pie for -pie.
	* plugin.c (set_tv_header <LDPT_LINKER_OUTPUT>): Simplify.