Bump version to 0.7 (709) and update changelog

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
external: Limit "make refresh" commits to openconnect binaries

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
external: Update from NDK r9 -> r9d

Probably doesn't make much of a difference, but r9 is getting a little
out-of-date.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>