Improve handling of > operator, preventing post-release from satisfying most rpm requirements.
Improve handling of < operator, preventing pre-release from satisfying rpm requirement.
Improve handling of != operator with prefix matching, preventing pre-release from satisfying rpm requirements.
This change introduces code from pyreq2rpm, a tested set of
requirement conversion functions used in pyp2rpm and rpm's
pythondistdeps.
This adds support for the '~=' operator and wildcards.