find_my_exec/find_other_exec(). Remove passing of progname to these
functions as they can find that out from argv[0], which they already
have.
Make get_progname return const char *, and update all progname variables
to be const char *.
only remnant of this failed experiment is that the server will take
SET AUTOCOMMIT TO ON. Still TODO: provide some client-side autocommit
logic in libpq.