Add support for subjectAltName's otherName entity

Lack of otherName support break https connection to some servers:
CACert, for example, automatically adds an id-on-xmppAddr[1] object for
each subjectAltName.

This result in the following exception:
PyAsn1Error: TagSet(Tag(tagClass=0, tagFormat=0, tagId=6),
Tag(tagClass=128, tagFormat=32, tagId=0)) not in asn1Spec: GeneralName()

Other CA might do similar things...

[1]: RFC3920 (XMPP Core) section 5.1 & 5.1.1