Bump up PG_CONTROL_VERSION on HEAD

Hi all,

f3db7f16 has proved that it can be a bad idea to run pg_resetwal on a
data folder which does not match the version it has been compiled
with.

As of HEAD, PG_CONTROL_VERSION is still 1100:
$ pg_controldata | grep "pg_control version"
pg_control version number:            1100

Wouldn't it be better to bump it up to 1200?

Thanks,
--
Michael