1.0.6.38: thread and interrupt safe ADD/REMOVE-METHOD

1.0.6.38: thread and interrupt safe ADD/REMOVE-METHOD

 * ADD/REMOVE-METHOD need to grab the GF lock and disable interrupts.

 * ADD/REMOVE-DIRECT-METHOD, and SPECIALIZER-DIRECT-GENERIC-FUNCTIONS
   need a lock as well, but instead of adding per-specializer lock
   just use one global one: contention should be minimal here.

 * INTERN-EQL-SPECIALIZER needs a lock.

 * Fix non-threaded build.

 * Delete dead NAME variables from ADD/REMOVE-METHOD.

 * Tests.