add_fde_encoding. Remove need_relative.
* elf-eh-frame.c (extra_augmentation_string_bytes)
(extra_augmentation_data_bytes, size_of_output_cie_fde): New functions.
(_bfd_elf_discard_section_eh_frame): Consider changing the FDE encoding
in cases where the CIE has no existing 'R' augmentation. Use
size_of_output_cie_fde when assigning offsets. Use the final offset
as the new section size.
(_bfd_elf_eh_frame_section_offset): Remove need_relative handling.
Account for any extra augmentation bytes in the returned offset.
(_bfd_elf_write_section_eh_frame): Rework so that the entries are
moved before being modified. Pad growing entries with DW_CFA_nops.
Add 'z' and 'R' augmentations as directed by add_augmentation_size
and add_fde_encoding.
