win32: update Inno Setup installer script and extensions list

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branch : stable
import: cut commit messages at --- unconditionally (issue2148)

We used to do this based on X-mailer: mentioning git, but git doesn't
put X-mailer in its git-format-patch output.

--HG--
branch : stable
checklink: work around sshfs brain-damage (issue3636)

With the follow_symlinks option, sshfs will successfully create links
while claiming it encountered an I/O error. In addition, depending on
the type of link, it may subsequently be impossible to delete the link
via sshfs. Our existing link to '.' will cause sshfs to think the link
is a directory, and thus cause unlink to give EISDIR. Links to
non-existent names or circular links will cause the created link to not even
be visible.

Thus, we need to create a new temporary file and link to that. We'll
still get a failure, but we'll be able to remove the link.

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branch : stable