Allow configure to detect whether ndbm.h or gdbm/ndbm.h is installed.
This allows dbmmodule.c to use either without having to add additional
options to the Modules/Setup file or make source changes.

(At least some Linux systems use gdbm to emulate ndbm, but only install
the ndbm.h header as /usr/include/gdbm/ndbm.h.)
diff --git a/config.h.in b/config.h.in
index 72f4fbc..8616811 100644
--- a/config.h.in
+++ b/config.h.in
@@ -272,9 +272,6 @@
 /* The number of bytes in a void *.  */
 #undef SIZEOF_VOID_P
 
-/* Define if you have the _getpty function.  */
-#undef HAVE__GETPTY
-
 /* Define if you have the alarm function.  */
 #undef HAVE_ALARM
 
@@ -362,6 +359,9 @@
 /* Define if you have the getpid function.  */
 #undef HAVE_GETPID
 
+/* Define if you have the _getpty function.  */
+#undef HAVE__GETPTY
+
 /* Define if you have the getpwent function.  */
 #undef HAVE_GETPWENT
 
@@ -521,12 +521,12 @@
 /* Define if you have the waitpid function.  */
 #undef HAVE_WAITPID
 
-/* Define if you have the <db.h> header file.  */
-#undef HAVE_DB_H
-
 /* Define if you have the <db_185.h> header file.  */
 #undef HAVE_DB_185_H
 
+/* Define if you have the <db.h> header file.  */
+#undef HAVE_DB_H
+
 /* Define if you have the <dirent.h> header file.  */
 #undef HAVE_DIRENT_H
 
@@ -536,6 +536,9 @@
 /* Define if you have the <fcntl.h> header file.  */
 #undef HAVE_FCNTL_H
 
+/* Define if you have the <gdbm/ndbm.h> header file.  */
+#undef HAVE_GDBM_NDBM_H
+
 /* Define if you have the <libutil.h> header file.  */
 #undef HAVE_LIBUTIL_H
 
@@ -548,6 +551,9 @@
 /* Define if you have the <ncurses.h> header file.  */
 #undef HAVE_NCURSES_H
 
+/* Define if you have the <ndbm.h> header file.  */
+#undef HAVE_NDBM_H
+
 /* Define if you have the <ndir.h> header file.  */
 #undef HAVE_NDIR_H