Trent Mick points out that the BSD DB also provides an ndbm compatibility
layer. If that is available, consider that as an option as well.
diff --git a/configure.in b/configure.in
index af4056e..d36f312 100644
--- a/configure.in
+++ b/configure.in
@@ -371,7 +371,8 @@
signal.h stdarg.h stddef.h stdlib.h thread.h unistd.h utime.h \
sys/audioio.h sys/file.h sys/lock.h db_185.h db.h \
sys/param.h sys/select.h sys/socket.h sys/time.h sys/times.h \
-sys/un.h sys/utsname.h sys/wait.h pty.h libutil.h ndbm.h gdbm/ndbm.h)
+sys/un.h sys/utsname.h sys/wait.h pty.h libutil.h \
+ndbm.h db1/ndbm.h gdbm/ndbm.h)
AC_HEADER_DIRENT
# checks for typedefs