fix compilation of commoncrypto backend under 10.8
add 0.5.2 changelog to master (backport from 0.5.x branch)
Merge pull request #1237 from reaperhulk/fix-1229

fix compilation of commoncrypto backend under 10.8
Merge pull request #1242 from reaperhulk/update-052-changelog

add 0.5.2 changelog to master (backport from 0.5.x branch)
Add a sensible repr to RSAPublicNumbers