Work around bug where Linux libc's have Berekeley DB 2 in them

Work around bug where Linux libc's have Berekeley DB 2 in them
       Patch by Paul Marquess <Paul.Marquess@btinternet.com>,
       DB_File's maintainer. His description:

The patch is to work around a problem where some versions of
Linux have a C library with Berkeley DB version 2 embedded in
it. This makes life difficult if you want to build with a
version of Berkeley DB other than the one embedded in
libc. This problem is compounded by the way Perl used to
*always* include the Berkeley DB library when it was being
built. The DB_File patches solves the latter problem, by
retrofitting the fix to Configure et al that was included from
perl 5.6 on. I think your best course of action is to just
apply the 5.00503 patch to the 5.00504 source. I just tried
applying it and it seems ok.

p4raw-id: //depot/maint-5.005/perl@22065