Edit .eh_frame symbols

Edit .eh_frame symbols

Experimental support for moving symbols defined in .eh_frame as their
CIEs/FDEs are edited or merged.

	* elf-bfd.h (struct eh_cie_fde): Add aug_str_len and aug_data_len.
	(_bfd_elf_adjust_eh_frame_global_symbol): Declare.
	* elf-eh-frame.c (_bfd_elf_parse_eh_frame): Set aug_str_len and
	aug_data_len.
	(offset_adjust): New function.
	(_bfd_elf_adjust_eh_frame_global_symbol): Likewise.
	(adjust_eh_frame_local_symbols): Likewise.
	(_bfd_elf_discard_section_eh_frame): Call adjust_eh_frame_local_symbols
	after changing anything.  Return true if anything changed.
	* elflink.c (bfd_elf_discard_info): If .eh_frame changed, call
	_bfd_elf_adjust_eh_frame_global_symbol for globals.