Implement sincos using the new Lisp trig routines. This can now be

used for all platforms.

 code/irrat.lisp::
 * Implement %SINCOS

 compiler/float-tran.lisp::
 * Update deftransforms for CIS.  %SINCOS can be used on any platform.

 tests/trig.lisp:
 * Add tests to verify %sincos returns exactly the same values as for
   sin and cos.