remove superfluous OPERATION-DONE-P method on TEST-OP
load the test system instead of testing it
whitespace
more WITH-CUDA -> WITH-CUDA* renames
mark up some code blocks properly
make WITH-FACET interrupt safe
allow nesting of WITH-FACETs for the same facet

This used to signal an error:

    (with-facet (a (m 'array :direction :input))
      (with-facet (a (m 'array :direction :io))
        ...))

Not anymore. This allow unsuspecting, general purpose functions (think
AXPY!) to correctly deal with cases where some of the arguments are
the same MAT object (as in (AXPY! 1 X X)).

Nesting WITH-FACETs for different facets is still an error and so is
having a read/write conflict between threads.
simplify .*!
make MATs thread safe by default

Opt out with :SYNCHRONIZATION, *DEFAULT-SYNCHRONIZATION*,
and *MAYBE-SYNCHRONIZE-CUBE*.
document accessor initargs and initform