Add transaction barriers
These allow packages to be installed and removed which have scripts
that depend on each other when atomic transactions are involved.
Note that yum supports pre, but not other requires flags. post will
need similar support to the post scripts themselves pulling in the
requires flags from the rpms. Likewise preun and postun will need
similar handling to those scrips since the requires flags will need
to be stored in the razor database.

 #!/bin/sh

 export RAZOR_ROOT=`mktemp -dt` || exit 1

 ../src/razor init || exit 1

 export YUM_URL="file://localhost/`pwd`"

 ../src/razor import-yum || exit 1

 ../src/razor install zsh2 || exit 1

 ../src/razor info zsh2 > details.out || exit 1

 diff -u $srcdir/details.ref details.out || exit 1

 rm -rf "$RAZOR_ROOT"