Previously, Eshell would get confused and think the following command
was unterminated due to the second double-quote looking like it was
escaped:
echo "\\"
* lisp/eshell/esh-util.el (eshell-find-delimiter): Correct docstring
and treat '\' as an escapeable character when using backslash escapes.
* test/lisp/eshell/eshell-tests.el
(eshell-test/escape-special-quoted): Adapt test.