better inner and anonymous function names

better inner and anonymous function names

 * New concept: "name context". It is either name of the outermost non-NIL
   block in the current lexenv (FIXME: would be better to have the outermost
   global function name instead) or the source-namestring of the file in which
   the function resides.

 * Name anonymous functions as

    (LAMBDA <lambda-list> :IN <context>)

 * Name FLET and LABELS functions as

    (FLET <name> :IN <context>)

   and

    (LABELS <name> :IN <context>)

   Adjust tests to suit.

 * Remove BLOCK-GENSYM as this fulfills the same goals, and together
   they make backtraces overly noisy.