Kai Uwe Rommel's port of GNU GDBM required several build changes:

- build with support for linking to multithreaded apps;
- include gdbmexists.o file into the library, as its needed by Python's 
  gdbm module.

Andrew MacIntyre
<andymac@bullseye.apana.org.au>
<andymac@pcug.org.au>
March 26, 2001
