SetuptoolsEggMetadata.from_egg does not respect the platform abi of the eggs

[itziakos]

The from_egg constructor will ignore the platform abi info commonly encoded in the name of setuptools eggs in favor of the EPDPlatform instance passed into the constructor. So it is possible for example to create SetuptoolEggMetadata instances of a linux egg that claims the egg is a windows 32 bit binary egg.

Ideally okonomiyaki should be able to tell if the setuptools egg platform is compatible with the passed EPDPlatform instance, but at least I would expect that if the passed EPDPlatform instance declares a different platform abi than the discovered (if available) encoded in the name, then a warning is raised to notify the users of possible issues.