bug#27995: view-lossage should show the contents of prompts

[積丹尼 Dan Jacobson]

C-h l runs the command view-lossage.

It is great, however an improvement would be to show what the user was
prompted with.

Why? Because hitting RET is equivalent to the user typing what he was
prompted with, however the latter is never recorded.

C-x 4 b [switch-to-buffer-other-window] #prompted with mno321
 <return> [minibuffer-complete-and-exit]

 C-x k [kill-buffer]                     #prompted with xyz123
 <return> [minibuffer-complete-and-exit]

Indeed even open-dribble-file doesn't capture the prompts, nor does
C-h e which runs the command view-echo-area-messages.