(Fdefine_key): Allow symbol as KEY argument for

(Fdefine_key): Allow symbol as KEY argument for
defining command remapping.  Doc updated.
(Flookup_key): Remap command through keymap if KEY is a symbol.
(is_command_symbol): New function.
(Fkey_binding): Use it.  New optional argument NO-REMAP.  Doc
updated.  Callers changed.  Perform command remapping via
recursive call unless that arg is non-nil.
(where_is_internal): New argument no_remap.  Callers changed.
Call recursively to find original key bindings for a remapped
comand unless that arg is non-nil.
(Fwhere_is_internal): New optional argument NO-REMAP.  Doc
updated.  Callers changed.  Pass arg to where_is_internal.