* coffread.c (cs_to_section): Use gdb_bfd_section_index.

	* coffread.c (cs_to_section): Use gdb_bfd_section_index.
	* elfread.c (record_minimal_symbol, elf_symtab_read): Use
	gdb_bfd_section_index.
	* gdb_bfd.c (gdb_bfd_section_index, gdb_bfd_count_sections):
	New functions.
	* gdb_bfd.h (gdb_bfd_section_index, gdb_bfd_count_sections):
	Declare.
	* machoread.c (macho_symtab_add_minsym, macho_symfile_offsets):
	Update.
	* objfiles.c (add_to_objfile_sections_full): New function.
	(add_to_objfile_sections): Use it.
	(build_section_table): Rewrite.
	(objfile_relocate1): Use gdb_bfd_section_index.  Update.
	* objfiles.h (obj_section_offset): Use gdb_bfd_section_index.
	(struct objfile) <sections>: Update comment.
	(ALL_OBJFILE_OSECTIONS): Skip sections where the_bfd_section
	is NULL.
	(ALL_OBJSECTIONS): Use it.
	* solib-dsbt.c (dsbt_relocate_main_executable): Update.
	* solib-frv.c (frv_relocate_main_executable): Update.
	* solib-target.c (solib_target_relocate_section_addresses):
	Use gdb_bfd_section_index.
	* symfile.c (build_section_addr_info_from_section_table):
	Use gdb_bfd_section_index.
	(build_section_addr_info_from_bfd, place_section): Likewise.
	* symtab.c (fixup_section): Update.
	* xcoffread.c (find_targ_sec): Use gdb_bfd_section_index.