Fix configure's search for collateindex.pl.

PGAC_PATH_COLLATEINDEX supposed that it could use AC_PATH_PROGS to search
for collateindex.pl, but that macro will only accept files that are marked
executable, and at least some DocBook installations don't mark the script
executable (a case the docs Makefile was already prepared for).  Accept the
script if it's present and readable in $DOCBOOKSTYLE/bin, and otherwise
search the PATH as before.

Having fixed that up, we don't need the fallback case that was in the docs
Makefile, and instead can throw an understandable error if configure didn't
find the script.  Per recent trouble report from John Lumby.

config/docbook.m4

@@ -89,11 +89,14 @@ fi])# PGAC_PATH_DOCBOOK_STYLESHEETS
 
 # PGAC_PATH_COLLATEINDEX
 # ----------------------
+# Some DocBook installations provide collateindex.pl in $DOCBOOKSTYLE/bin,
+# but it's not necessarily marked executable, so we can't use AC_PATH_PROG
+# to check for it there.  Other installations just put it in the PATH.
 AC_DEFUN([PGAC_PATH_COLLATEINDEX],
 [AC_REQUIRE([PGAC_PATH_DOCBOOK_STYLESHEETS])dnl
-if test -n "$DOCBOOKSTYLE"; then
-  AC_PATH_PROGS(COLLATEINDEX, collateindex.pl, [],
-                [$DOCBOOKSTYLE/bin $PATH])
+if test -n "$DOCBOOKSTYLE" -a -r "$DOCBOOKSTYLE/bin/collateindex.pl"; then
+  COLLATEINDEX="$DOCBOOKSTYLE/bin/collateindex.pl"
+  AC_SUBST([COLLATEINDEX])
 else
-  AC_PATH_PROGS(COLLATEINDEX, collateindex.pl)
+  AC_PATH_PROG(COLLATEINDEX, collateindex.pl)
 fi])# PGAC_PATH_COLLATEINDEX

configure

@@ -29430,57 +29430,12 @@ else
   { $as_echo "$as_me:$LINENO: result: no" >&5
 $as_echo "no" >&6; }
 fi
-if test -n "$DOCBOOKSTYLE"; then
-  for ac_prog in collateindex.pl
-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:$LINENO: checking for $ac_word" >&5
-$as_echo_n "checking for $ac_word... " >&6; }
-if test "${ac_cv_path_COLLATEINDEX+set}" = set; then
-  $as_echo_n "(cached) " >&6
-else
-  case $COLLATEINDEX in
-  [\\/]* | ?:[\\/]*)
-  ac_cv_path_COLLATEINDEX="$COLLATEINDEX" # Let the user override the test with a path.
-  ;;
-  *)
-  as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
-for as_dir in $DOCBOOKSTYLE/bin $PATH
-do
-  IFS=$as_save_IFS
-  test -z "$as_dir" && as_dir=.
-  for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
-    ac_cv_path_COLLATEINDEX="$as_dir/$ac_word$ac_exec_ext"
-    $as_echo "$as_me:$LINENO: found $as_dir/$ac_word$ac_exec_ext" >&5
-    break 2
-  fi
-done
-done
-IFS=$as_save_IFS
+if test -n "$DOCBOOKSTYLE" -a -r "$DOCBOOKSTYLE/bin/collateindex.pl"; then
+  COLLATEINDEX="$DOCBOOKSTYLE/bin/collateindex.pl"
 
-  ;;
-esac
-fi
-COLLATEINDEX=$ac_cv_path_COLLATEINDEX
-if test -n "$COLLATEINDEX"; then
-  { $as_echo "$as_me:$LINENO: result: $COLLATEINDEX" >&5
-$as_echo "$COLLATEINDEX" >&6; }
 else
-  { $as_echo "$as_me:$LINENO: result: no" >&5
-$as_echo "no" >&6; }
-fi
-
-
-  test -n "$COLLATEINDEX" && break
-done
-
-else
-  for ac_prog in collateindex.pl
-do
-  # Extract the first word of "$ac_prog", so it can be a program name with args.
-set dummy $ac_prog; ac_word=$2
+  # Extract the first word of "collateindex.pl", so it can be a program name with args.
+set dummy collateindex.pl; ac_word=$2
 { $as_echo "$as_me:$LINENO: checking for $ac_word" >&5
 $as_echo_n "checking for $ac_word... " >&6; }
 if test "${ac_cv_path_COLLATEINDEX+set}" = set; then
@@ -29519,9 +29474,6 @@ $as_echo "no" >&6; }
 fi
 
 
-  test -n "$COLLATEINDEX" && break
-done
-
 fi
 for ac_prog in xsltproc
 do

doc/src/sgml/Makefile

@@ -27,10 +27,6 @@ all: html man
 distprep: html distprep-man
 
 
-ifndef COLLATEINDEX
-COLLATEINDEX = $(DOCBOOKSTYLE)/bin/collateindex.pl
-endif
-
 ifndef JADE
 JADE = jade
 endif
@@ -120,7 +116,11 @@ HTML.index: postgres.sgml $(ALMOSTALLSGML) stylesheet.dsl
 	$(JADE.html.call) -V html-index $<
 
 bookindex.sgml: HTML.index
+ifdef COLLATEINDEX
 	LC_ALL=C $(PERL) $(COLLATEINDEX) -f -g -i 'bookindex' -o $@ $<
+else
+	@$(missing) collateindex.pl $< $@
+endif
 
 # Technically, this should depend on Makefile.global, but then
 # version.sgml would need to be rebuilt after every configure run,