sbcl-pwd.sh: Fix when $OSTYPE is not set.
Optimize RESTART-CASE.

Optimize a case when restart handlers have zero or one arguments:
instead of saving a &rest list and then applying a function, don't
save anything, or save one argument and use FUNCALL.

Based on a patch by Jan Moringen.

Closes lp#1249055.
Optimize RESTART-BIND.

Change MAKE-RESTART lambda-list to
(name function
 &optional report-function interactive-function test-function)
instead of using the default structure constructor with keywords.
MAKE-RESTART is only used in RESTART-BIND, and this allows for more
compact calls and not having to parse keyword parameters should
make the code slightly faster.
Optimize testing of sealed structures.

Don't check for the layout validity, redefining structures is
undefined, and the non-sealed case doesn't check for it already.