Make --without-docdir configure option actually work, per Manfred.

src/Makefile.global.in

 # -*-makefile-*-
-# $PostgreSQL: pgsql/src/Makefile.global.in,v 1.187 2004/05/22 00:34:49 tgl Exp $
+# $PostgreSQL: pgsql/src/Makefile.global.in,v 1.188 2004/05/23 15:24:32 tgl Exp $
 
 #------------------------------------------------------------------------------
 # All PostgreSQL makefiles include this file and use the variables it sets,
@@ -105,11 +105,14 @@ mandir := @mandir@
 sqlmansect_dummy = l
 
 docdir := @docdir@
+# docdir can be an empty string to signify --without-docdir
+ifneq (,$(docdir))
 ifeq "$(findstring pgsql, $(docdir))" ""
 ifeq "$(findstring postgres, $(docdir))" ""
 override docdir := $(docdir)/postgresql
 endif
 endif
+endif
 
 localedir := @localedir@