Remove the autoconf checks for etags/ctags and `make tags` target

There's no strong reason to keep `make tags` in our build system.  The previous
functionality of `make tags` could be simply retained by aliasing variant of:

    etags $(git ls-files '*.c' '*.h')

which would be universal for all C-code projects.

Makefile.in

@@ -56,10 +56,6 @@ install:: installdirs
 uninstall::
 	rm -f ${DESTDIR}${sysconfdir}/bind.keys
 
-tags:
-	rm -f TAGS
-	find lib bin -name "*.[ch]" -print | @ETAGS@ -
-
 test check:
 	@if test -n "`${PERL} ${top_srcdir}/bin/tests/system/testsock.pl 2>/dev/null || echo fail`"; then \
 	echo I: NOTE: The tests were not run because they require that; \

configure

@@ -769,7 +769,6 @@ COVERAGE
 CHECKDS
 PYTHON
 PERL
-ETAGS
 LN
 ARFLAGS
 XTARGETS
@@ -12413,73 +12412,6 @@ which ar resides, or set AR in the environment with the full path to ar.
 		;;
 esac
 
-#
-# Etags.
-#
-for ac_prog in etags emacs-etags
-do
-  # Extract the first word of "$ac_prog", so it can be a program name with args.
-set dummy $ac_prog; ac_word=$2
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
-$as_echo_n "checking for $ac_word... " >&6; }
-if ${ac_cv_path_ETAGS+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  case $ETAGS in
-  [\\/]* | ?:[\\/]*)
-  ac_cv_path_ETAGS="$ETAGS" # Let the user override the test with a path.
-  ;;
-  *)
-  as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
-for as_dir in $PATH
-do
-  IFS=$as_save_IFS
-  test -z "$as_dir" && as_dir=.
-    for ac_exec_ext in '' $ac_executable_extensions; do
-  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
-    ac_cv_path_ETAGS="$as_dir/$ac_word$ac_exec_ext"
-    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
-    break 2
-  fi
-done
-  done
-IFS=$as_save_IFS
-
-  ;;
-esac
-fi
-ETAGS=$ac_cv_path_ETAGS
-if test -n "$ETAGS"; then
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ETAGS" >&5
-$as_echo "$ETAGS" >&6; }
-else
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
-$as_echo "no" >&6; }
-fi
-
-
-  test -n "$ETAGS" && break
-done
-
-
-#
-# Some systems, e.g. RH7, have the Exuberant Ctags etags instead of
-# GNU emacs etags, and it requires the -L flag.
-#
-if test "X$ETAGS" != "X"; then
-	{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for Exuberant Ctags etags" >&5
-$as_echo_n "checking for Exuberant Ctags etags... " >&6; }
-	if $ETAGS --version 2>&1 | grep 'Exuberant Ctags' >/dev/null 2>&1; then
-		{ $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
-$as_echo "yes" >&6; }
-		ETAGS="$ETAGS -L"
-	else
-		{ $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
-$as_echo "no" >&6; }
-	fi
-fi
-
-
 #
 # Perl is optional; it is used only by some of the system test scripts.
 # Note: the backtrace feature (see below) uses perl to build the symbol table,

configure.ac

@@ -180,26 +180,6 @@ which ar resides, or set AR in the environment with the full path to ar.
 		;;
 esac
 
-#
-# Etags.
-#
-AC_PATH_PROGS(ETAGS, etags emacs-etags)
-
-#
-# Some systems, e.g. RH7, have the Exuberant Ctags etags instead of
-# GNU emacs etags, and it requires the -L flag.
-#
-if test "X$ETAGS" != "X"; then
-	AC_MSG_CHECKING(for Exuberant Ctags etags)
-	if $ETAGS --version 2>&1 | grep 'Exuberant Ctags' >/dev/null 2>&1; then
-		AC_MSG_RESULT(yes)
-		ETAGS="$ETAGS -L"
-	else
-		AC_MSG_RESULT(no)
-	fi
-fi
-AC_SUBST(ETAGS)
-
 #
 # Perl is optional; it is used only by some of the system test scripts.
 # Note: the backtrace feature (see below) uses perl to build the symbol table,