gen-meta-support: reverse XML entity sorting

This prevents us from having to loop over all of the XML entities for
every single MetadataStore call.  Total run time is reduced from ~20
minutes locally to ~11 minutes.

Conflicts:

	components/autogen/src/gen-meta-support.sh
Merge pull request #599 from melissalinkert/autogen-performance-dev_4_4

gen-meta-support: reverse XML entity sorting