vty: Add ctrl-v <literal> to allow, e.g., '?' to be input for regex

* Support the standard ctrl-v <literal> control sequence. Otherwise there
  is no way to do this from the venerable telnet vty. vtysh supports this
  (configurably) via readline.
* lib/vty.c: (VTY_ESC_LITERAL) New mode, for ctrl-v.
  (vty_read) Additional mode to go ctrl-v -> VTY_ESC_LITERAL, and
  always insert next char.

Acked-by: Vincent.Jardin@6wind.com
2 files changed