1.0.42.46: style-warn users about READ-FROM-STRING &optional gotcha

1.0.42.46: style-warn users about READ-FROM-STRING &optional gotcha

 Check -- at runtime if need be! -- if the EOF-ERROR-P argument to
 READ-FROM-STRING is one of its keyword arguments, and signal a
 style-warning explaining the issue if so,

 Since the runtime check surprisingly has a measurable cost, add a
 compiler-macro that

  * signals the style-warning at compile-time.

  * rewrites the call into required-args-only form.

 Which actually nets us a 2% speedup... perhaps we should consider
 more widespread rewriting of &KEY calls into required-args-only form.