The docstring of evil-cursor-back only mentions that it applies to moving the
cursor back when exiting insert state, but in many cases it was tied to also
moving the cursor when reaching the end of the line. We have
evil-move-beyond-eol to control that behavior, and there doesn't seem to be a
good reason that the two must be tied together.

Fixes #1178

evil-delimited-arguments might drop characters from the chained
command if the input ends with a trailing slash (so in something like
:g/pattern/s/pat/repl/, the /pat/repl/ part gets dropped). Since the
chained command follows after the slash following the pattern, we can
just take a substring instead of relying on `evil-delimited-arguments`
for it.

pattern is an object. We need to get the regex first.

See #832

With the ex command :s/^/ /, the pattern will match the beginning of the current
line and the next line in evil-ex-hl-update-highlights when it should only match
the beginning of the current line.