Put `C-h' bindings that access Info on a common prefix key

[Drew Adams]

After the release:

Why not put all `C-h' commands that access Info on a prefix key: `C-h C-i'?

Currently, we have these bindings for such commands:

 `C-h F' - Info-goto-emacs-command-node
 `C-h r' - info-emacs-manual
 `C-h S' - info-lookup-symbol

These are mixed in with other `C-h' commands that don't access Info - `C-h
f' describes a command (function), and `C-h F' looks it up in the manual.

I think it would be tidier, and probably more convenient (easier to
remember), to put all of these on the prefix `C-h C-i'. For one thing, that
would free up keys for other possible help commands. For another, we could
pick better mnemonics - `k' for key (Info-goto-emacs-key-command-node), `c'
for command (Info-goto-emacs-command-node), `h' for help (info-help), `f'
for file (info-lookup-file), `e' for Emacs (info-emacs-manual)...

The current mnemonics are not that great, and they can confuse people (`s'
for syntax, `S' for symbol - not the same relation as `f' and `F'). Since
Info commands form a subclass of the help commands, let's give them their
own (sub) prefix key.

WDOT?