1.0.21.21: manpage "improvements"

1.0.21.21: manpage "improvements"

 * Describe what SBCL is in terms of its capabilities, not ancestry.
   (A little hype never hurts...)

 * Join the DESCRIPTION and LICENCING sections to save vertical space.

 * Simplify the language in RUNNING SBCL, and stick in a pointer to
   SAVE-LISP-AND-DIE with reference to standalone executables.

 * Move the COMMAND LINE SYNTAX section waaay up, so that one doesn't
   have to scroll several screenfulls to get to it.

 * Move the DIFFERENCES FROM CMU CL waaay down, and delete the list of
   deleted extensions.

 * Remove the FUD about CLOS efficiency from known bugs.