[Bug-readline] buggy interaction between bracketed-paste mode and vi mode

[vampyrebat]

I am running readline 7.0 on a Gentoo Linux system.  I am using GNU bash 
version 4.4.23.  There is a bug in the way bracketed-paste mode interacts with 
vi mode.

You can demonstrate this as follows:

1. Start a fresh bash, with no .inputrc (and no /etc/inputrc, just to be sure 
you have readline's default configuration).

2. Enter the command: set -o vi

3. With the mouse, select/copy the letter "o" from the above command.

4. Type "jibs" (but do not press RETURN).

5. Change the "i" to an "o" by pressing ESC, pressing "h" twice, pressing "r", 
and finally using the mouse to paste the previously selected letter "o".
   - The "i" changes to an "o" as expected, and when you press RETURN, bash 
runs the command.

6. Enter the command: bind 'set enable-bracketed-paste on'

7. Repeat steps 3 to 5 above.
   - Step 5 now fails: instead of replacing the letter "i", readline changes 
the case of the entire rest of the line (so that it now reads "jIBS").

This same (mis)behavior occurs using the uppercase-R command in vi mode for any 
number of alphanumeric characters.

bracketed-paste mode should not affect the pasting of alphanumeric characters 
that do not include newlines and that would, if typed directly, be entered on 
the command line exactly as seen.  (That is, this behavior does nothing to 
"prevent pasted characters from being interpreted as editing commands," which 
is all bracketed-paste mode is supposed to do, per the man page).