shell-backward-kill-word needs to behave more like werase

[Basin Ilya]

The default werase setting erases the series of white spaces before the caret, 
then it erases the preceding word (without touching the spaces before the word).
I expected that shell-backward-kill-word would do the same with the difference 
that the entire quoted argument would be erased.
However, shell-backward-kill-word erases the word immedeately preceding the 
caret plus it erases one additional space. This causes the inconvenience that 
after erasing the shell word you can't immediately type a new word. You have to 
type again a space that was deleted. I tried to restore the missing space using 
sequence of commands, but it restores an unwanted space after erasing the very 
first word:

    stty werase undef
    bind '"\C-\xff": delete-horizontal-space' # erase whitespaces following the 
word
    bind '"\C-\xfe": shell-backward-kill-word' # erase the word
    bind '"\C-w": "\C-\xff\C-\xfe "' # erase whitespaces, erase word, restore 1 
space