binutils, ld: work with --disable-libctf

This unfortunately means conditionalizing out all the libctf code, but
the result is not too unbearably ugly, if a bit repetitive.  I have
stubbed out code in the !ENABLE_LIBCTF path to avoid extra redundant
ifdefs where it seems that might be helpful.  (The stubs are not too
disruptive, but I've tried to keep them on one line where possible to
avoid filling up the screen with stubs that nobody would care about.
If this is too much of a coding style violation I can change it.)

Changes since v2: use GCC_ENABLE rather than repeating all the
                  AC_ARG_ENABLE stuff over and over again.

ld/
	* configure.ac [--enable-libctf]: New, default yes.
	Set ENABLE_LIBCTF accordingly.
	* Makefile.am [!ENABLE_LIBCTF]: Empty LIBCTF.
	* configure: Regenerate.
	* config.in: Regenerate.
	* Makefile.in: Regenerate.
	* aclocal.m4: Regenerate.
	* ldlang.c (ctf_output): Conditionalize on ENABLE_LIBCTF.
	(ldlang_open_ctf): Likewise.
	(lang_merge_ctf): Likewise.
	(ldlang_ctf_apply_strsym): Likewise.
	(lang_write_ctf): Likewise.
	(ldlang_write_ctf_late): Likewise.
	(ldlang_open_ctf) [!ENABLE_LIBCTF]: Warn about the presence of CTF
	sections.
	(lang_merge_ctf) [!ENABLE_LIBCTF]: New stub.
	(ldlang_ctf_apply_strsym) [!ENABLE_LIBCTF]: Likewise.
	(lang_write_ctf) [!ENABLE_LIBCTF]: Likewise.
	(ldlang_write_ctf_late) [!ENABLE_LIBCTF]: Likewise.
	* ldelfgen.c (ldelf_emit_ctf_early): Conditionalize on
	ENABLE_LIBCTF.
	(struct ctf_strsym_iter_cb_arg): Likewise.
	(ldelf_ctf_strtab_iter_cb): Likewise.
	(ldelf_ctf_symbols_iter_cb): Likewise.
	(ldelf_examine_strtab_for_ctf): Likewise.
	(ldelf_emit_ctf_early) [!ENABLE_LIBCTF]: New stub.
	(ldelf_examine_strtab_for_ctf) [!ENABLE_LIBCTF]: New stub.

binutils/
	* configure.ac [--enable-libctf]: New, default yes.
	Set ENABLE_LIBCTF accordingly.
	* Makefile.am [!ENABLE_LIBCTF]: Empty LIBCTF and LIBCTF_NOBFD.
	* configure: Regenerate.
	* config.in: Regenerate.
	* Makefile.in: Regenerate.
	* aclocal.m4: Regenerate.
	* objdump.c (usage): Conditionalize portions on ENABLE_LIBCTF.
	(option_values): Likewise.
	(long_options): Likewise.
	(main): Likewise.
	(dump_ctf_indent_lines): Conditionalize out when !ENABLE_LIBCTF.
	(make_ctfsect): Likewise.
	(dump_ctf_archive_member): Likewise.
	(dump_ctf) [ENABLE_LIBCTF]: Likewise.
	(dump_ctf) [!ENABLE_LIBCTF]: New empty stub.
	* readelf.c (options): Conditionalize portions on ENABLE_LIBCTF.
	(usage): Likewise.
	(process_section_contents): Likewise.
	(shdr_to_ctf_sect): Conditionalize out when !ENABLE_LIBCTF.
	(dump_ctf_indent_lines): Likewise.
	(dump_section_as_ctf) [ENABLE_LIBCTF]: Likewise.