configure: check for additional ctags names

It looks like it's been assumed that "ctags" is exuberant ctags
(or similar), but some systems like OpenBSD have a ctags in the
base system that does not support some desired options like -R.
Try some other names first.

src/Makefile.in

@@ -32,6 +32,7 @@ LDFLAGS	= @LDFLAGS@
 RM	= @RM@
 LN_S	= @LN_S@
 EXE	= @EXEEXT@
+CTAGS	= @CTAGS@
 ETAGS	= @ETAGS@
 RANLIB	= @RANLIB@
 AR	= @AR@
@@ -293,7 +294,7 @@ selfbuild:
 	-for i in lsp clos cmp tk; do test -d $$i && diff --exclude=\*.o $$i stage2/$$i; done | less
 
 .git/tags:
-	( cd $(srcdir)/../.git && which ctags && ctags -f tags -R --langmap=c:+.d ../src ) || echo "tags generation failed, but this does not break the build."
+	( cd $(srcdir)/../.git && test "x$(CTAGS)" != "x" && $(CTAGS) -f tags -R --langmap=c:+.d ../src ) || echo "tags generation failed, but this does not break the build."
 
 # Make sure to also include *.d files; and match DPP's idiosyncracies
 # like "@si::foo" and "@(defun si::foo".  This rule is allowed to fail

src/configure

@@ -674,6 +674,7 @@ CP
 true_builddir
 true_srcdir
 ETAGS
+CTAGS
 AR
 SET_MAKE
 LN_S
@@ -4721,6 +4722,48 @@ else
   AR="$ac_cv_prog_AR"
 fi
  # set variable AR to appropriate `ar' program
+for ac_prog in exctags ectags ctags
+do
+  # Extract the first word of "$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_prog_CTAGS+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  if test -n "$CTAGS"; then
+  ac_cv_prog_CTAGS="$CTAGS" # Let the user override the test.
+else
+as_save_IFS=$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_prog_CTAGS="$ac_prog"
+    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
+    break 2
+  fi
+done
+  done
+IFS=$as_save_IFS
+
+fi
+fi
+CTAGS=$ac_cv_prog_CTAGS
+if test -n "$CTAGS"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $CTAGS" >&5
+$as_echo "$CTAGS" >&6; }
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
+
+  test -n "$CTAGS" && break
+done
+ # set variable CTAGS to ctags program if found
 for ac_prog in etags emacs-etags
 do
   # Extract the first word of "$ac_prog", so it can be a program name with args.

src/configure.ac

@@ -368,6 +368,7 @@ AC_PROG_LN_S          # sets variable LN_S
 AC_PROG_MAKE_SET      # set $(MAKE) if needed
 AC_PROG_RANLIB        # set variable RANLIB
 AC_CHECK_TOOL([AR],[ar]) # set variable AR to appropriate `ar' program
+AC_CHECK_PROGS([CTAGS],[exctags ectags ctags]) # set variable CTAGS to ctags program if found
 AC_CHECK_PROGS([ETAGS],[etags emacs-etags]) # set variable ETAGS to etags program if found
 
 dnl -----------------------------------------------------------------------