* NEWS: Document new options "set/show use-deprecated-index-sections",

	* NEWS: Document new options "set/show use-deprecated-index-sections",
	and delete reference to --use-deprecated-index-sections.
	* symfile.h (use_deprecated_index_sections): Delete.
	* dwarf2read.c (use_deprecated_index_sections): Make static.
	(read_index_from_section): Update wording of how to load
	deprecated index sections.
	(_initialize_dwarf2_read): New options
	"set/show use-deprecated-index-sections".
	* main.c (captured_main): Delete --use-deprecated-index-sections.

	doc/
	* gdb.texinfo (Mode Options): Delete --use-deprecated-index-sections.
	(Index Files): Document how to control the use of deprecated index
	sections.
	(Index Section Format): Replace --use-deprecated-index-sections with
	"set use-deprecated-index-sections on".