1.0.26.10: darwin interrupt fixes

1.0.26.10: darwin interrupt fixes

Work around raise(signal) apparently not raising the signal under some
circumstances. See sbcl-devel thread "Hang in tests on Intel MacOS
10.5.6" starting on 2009-03-14.

Also, block all blockables when in install_handler, having just one of
the signals blocked breaks invariants (not really darwin specific).

Replace abort() after the call mach_msg_server() with more a
informative lose(). It's actually returns after attaching and
detaching gdb.