Add support for RFC 4334 and fix errata for RFC 3770

[russhousley]

First, add module and test for RFC 4334 providing Certificate Extensions and Attributes for Authentication in PPP and Wireless LAN Networks. Note that RFC 4334 obsoletes RFC 3770.

Second, update RFC 3770 to support openType for attributes and handle the reported errata.

[codecov-io]

Codecov Report

Merging #105 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #105      +/-   ##
==========================================
+ Coverage   99.37%   99.38%   +<.01%     
==========================================
  Files          97       98       +1     
  Lines        5967     5989      +22     
==========================================
+ Hits         5930     5952      +22     
  Misses         37       37

Impacted Files	Coverage Δ
pyasn1_modules/rfc4334.py	100% <100%> (ø)
pyasn1_modules/rfc3770.py	100% <100%> (ø)	⬆️

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[etingof]

Thank you!