Teach rpm about pre-transaction dependencies
- A pre-transaction dependency is generally anything that must be
available at the start of the transaction, and cannot be resolved
by packages *in* the transaction. This lets %pretrans scriptlet
dependencies be expressed correctly, and could be also used for
other kinds of pre-conditions.
- rpmlib() dependencies are a special case of pre-trans dependencies
but leaving them handled separately as they cannot be provided by
anything in rpmdb either, whereas pretrans dependencies can.