1.0.47.24: more conservative FTYPE proclamations

1.0.47.24: more conservative FTYPE proclamations

  Full warnings for changing FTYPE proclamations in the
  cross-compiler, and always a CERROR when the function is a known one
  and the new type is not a subtype of the old one.

  This necessitates the following changes:

  * Rewriting DEF-MATH-RTN not to use DEFINE-ALIEN-ROUTINE which
    proclaims its FTYPE.

  * Fix the DEFKNOWN for CLASSOID-NAME to match the DEFSTRUCT.

  * Fix STRING-OUTPUT-STREAM-ELEMENT-TYPE slot type, and DEFKNOWN
    result type.