Changes from Vince Vielhaber to allow the optional clauses of CREATE

Changes from Vince Vielhaber to allow the optional clauses of CREATE
USER and ALTER USER to appear in any order, not only the fixed order
they used to be required to appear in.
Also, some changes from Tom Lane to create a FULL option for VACUUM;
it doesn't do anything yet, but I needed to change many of the same
files to make that happen, so now seemed like a good time.