Index PowerPC64 linker generated .eh_frame in .eh_frame_hdr

Index PowerPC64 linker generated .eh_frame in .eh_frame_hdr

I noticed recently that .eh_frame FDEs generated by the linker for
call stubs and .glink weren't being indexed in .eh_frame_hdr, due to
bfd_elf_discard_info being run before the linker generated .eh_frame
sections were available for parsing.  This patch moves code around in
elf64-ppc.c and ppc64elf.em to avoid that problem.

Another problem fixed here is that --gc-sections parses .eh_frame
early, and the existing machinery allows only one go at parsing the
.eh_frame sections.  That resulted in the linker generated .eh_frame
CIEs not being merged and no .eh_frame_hdr index entries for those
FDEs.  It turns out that all the info from parsing .eh_frame is
attached to the section, so order of parsing isn't important, and
after parsing sec_info_type being set will prevent a section being
parsed again.  At least, when parsing doesn't hit an error.  So there
isn't really any need for "parsed_eh_frame".  "merge_cies" is also
redundant, which means _bfd_elf_{begin,end}_eh_frame_parsing can also
disappear.

bfd/
	* elf-bfd.h (struct eh_frame_hdr_info): Delete merge_cies and
	parsed_eh_frames.
	(_bfd_elf_begin_eh_frame_parsing): Delete.
	(_bfd_elf_end_eh_frame_parsing): Delete.
	* elf-eh-frame.c (_bfd_elf_begin_eh_frame_parsing): Delete.
	(_bfd_elf_end_eh_frame_parsing): Delete.
	(_bfd_elf_parse_eh_frame): Don't test parsed_eh_frame.  Test
	!info->relocatable in place of merge_cies.
	* elflink.c (bfd_elf_gc_sections, bfd_elf_discard_info): Adjust.
	* elf64-ppc.c (glink_eh_frame_cie): Pad to multiple of 8.
	(ppc64_elf_size_stubs): Likewise pad stub FDE.
	(ppc64_elf_build_stubs): Move code setting glink .eh_frame to..
	(ppc64_elf_size_stubs): ..here and..
	(ppc64_elf_finish_dynamic_sections): ..here.
ld/
	* emultempl/ppc64elf.em (gld${EMULATION_NAME}_after_allocation): Call
	bfd_elf_discard_info after generating glink .eh_frame.  Delete
	redundant test on ppc64_elf_setup_section_lists status.