'protect' used to be renamed to 'guard', after excluding 'guard'
from (scheme base). But that part is now gone. test.scm itself never
uses 'protect' directly. Remove it because it's not used.
Many still import (chibi), and as (scheme base) is somewhat more
expensive to load at present these are changed to cond-expand.
Many libraries also rely on (srfi 33), and these have been changed
to a cond-expand first trying (srfi 60) where available.
Also fixing a few portability concerns (duplicate imports of the
same binding), and adding a few libraries missing from lib-tests.scm.
