Generate docs from compat config.

We read compat config from an XML file, turn that into a HDF, and then
generate docs using a new template and existing macros as appropriate.
  https://mathewi.users.x20web.corp.google.com/www/compatchanges/offline-sdk/compatchanges.html

Test: m -j offline-sdk-docs
Bug: 144927670
Change-Id: I67dd3662a83538f769aa535979f2119b33e1326e
Exempt-From-Owner-Approval: ag/10107214 approved internally, have Dirk's permission.
3 files changed