1.0.48.3: source-locations from LOAD of source files, and EVAL-WHEN :COMPILE-TOPLEVEL

1.0.48.3: source-locations from LOAD of source files, and EVAL-WHEN :COMPILE-TOPLEVEL

  * Bind *SOURCE-INFO* and bind and populate *SOURCE-PATHS* in
    LOAD-AS-SOURCE.

  * EVAL-TLF provides a way to evaluate things while providing the
    toplevel form number. It also captures the current *SOURCE-INFO*
    and passes it onwards to be reused by ACTUALLY-COMPILE.

  * In ACTUALLY-COMPILE, when asked to reuse a source-info object,
    also retain the old *SOURCE-PATHS*.