[Bug-readline] Custom vi mode bindings causes problems with some builtin commands

[Carlos Pita]

Defining bindings for "operators" like d and c (v.g. daw and caw, see
the recipe below) wreaks havoc with the dd, cc, and <dot> (vi-redo)
commands in readline vi mode.

# The version number and release status of Readline (e.g., 4.2-release):

readline 6.3.008

# The machine and OS that it is running on:

Linux carlos 4.0.5-1-ARCH #1 SMP PREEMPT Sat Jun 6 18:37:49 CEST 2015
x86_64 GNU/Linux

# A recipe for recreating the bug reliably:

1. Put just this into .inputrc:

```
set editing-mode vi

set keymap vi-command
"caw": "bcw"
```

2. Try cc and <dot> commands.