renaming pg_resetxlog to pg_resetwal has broken pg_upgrade.

Upgrading from 9.6 to dev, I now get:

$ rm bisectdata -r ; bisect/bin/pg_ctl initdb -D bisectdata;
bisect/bin/pg_upgrade -b /usr/local/pgsql9_6/bin/ -B bisect/bin/ -d 96 -D
bisectdata/

check for "/usr/local/pgsql9_6/bin/pg_resetwal" failed: No such file or
directory

This looks somewhat complicated to fix. Should check_bin_dir test the old
cluster version, and make a deterministic check based on that? Or just
check for either spelling, and stash the successful result somewhere?

Culprit is here:

commit 85c11324cabaddcfaf3347df78555b30d27c5b5a
Author: Robert Haas <rhaas(at)postgresql(dot)org>
Date: Thu Feb 9 16:23:46 2017 -0500

Rename user-facing tools with "xlog" in the name to say "wal".

This means pg_receivexlog because pg_receivewal, pg_resetxlog
becomes pg_resetwal, and pg_xlogdump becomes pg_waldump.

Cheers,

Jeff