So far, deprecated APIs are only listed as CHANGES entry.  But
they are not listed in one place.  In this change, I gathered them
to docs as a list.
As a side effect, it makes CHANGES entry simple.

This allows builders to emit a final epilog message containing
information such as where resulting files can be found. This is only
emitted if the build was successful.

This allows us to remove this content from the 'make_mode' tool and
the legacy 'Makefile' and 'make.bat' templates. There's room for more
dramatic simplification of the former, but this will come later.

Signed-off-by: Stephen Finucane <stephen@that.guru>