(te-pass-through): Handle meta chars and non-char events.

(te-pass-through): Handle meta chars and non-char events.
(terminal-map, etc.): Use default bindings, not fillarray.
Make the maps sparse.
(terminal-meta-map): New map; lets us make ESC a prefix key.
(terminal-map): Bind ESC to terminal-meta-map.
(te-more-break-unread): Handle non-char as last-input-char.
(te-filter): Delete code that worked with meta-flag.
(terminal-emulator): Don't look at meta-flag.
(terminal-mode): Don't make meta-flag local.
(te-stty-string): Quote the args that have ^.  Add pass8.

Changes that esr made in the previous version but didn't describe in detail:

Some defvars moved.
Defvars added for many variables.
(te-stty-string): Specify the characters explicitly--not `stty dec'.