Currently, the berkeley databases resuses a lot of the same code for the
expressions of each version. This consolidates all of the build routines
similar to that of the linux kernel.
This patch also adds version 6 of BDB.
hire me...). There is a very small race between processes exiting
the environment and processes entering, such that the entering
process would incorrectly conclude that the exiting process had
died and recovery was necessary. However, this race was triggering
crashes on a daily basis in our build farm.
svn path=/nixpkgs/trunk/; revision=8712