Annotate CHANGES.rst with bug ids.
Annotate CHANGES.rst with bug ids.

kwlzn/pex,snyaggarwal/pex,pantsbuild/pex,URXtech/pex,sixninetynine/pex,sixninetynine/pex,jamesbroadhead/pex,mzdanieltest/pex,rouge8/pex,rouge8/pex,jsirois/pex,jsirois/pex,URXtech/pex,jamesbroadhead/pex,snyaggarwal/pex,pombredanne/pex,pombredanne/pex,mzdanieltest/pex,kwlzn/pex,pantsbuild/pex