vim: 8.0.1150 -> 8.0.1245

This update contains a lot of fixes that are too much to be summarized
here, so here is the upstream changelog (basically "git log"):

https://github.com/vim/vim/commits/v8.0.1250



The main reason for this bump is that I got annoyed by a bug that was
fixed in upstream version 8.0.1194, which caused a race condition during
vim startup when it's trying to retrieve background colors from the
terminal.

Sometimes it could happen that random commands are executed at Vim
startup (typically pasting the "" buffer) and after bisecting I've found
out that version 8.0.1194 indeed fixed this problem.

The reason why I'm updating to version 8.0.1250 is that when looking
through the Git log it contains a whole lot of fixes but no new
features, so I'd assume it's safe to upgrade.

I've tested all packages that depend on Vim and they still succeed
building. In addition to that I've used the new version for a couple of
hours without any issue.

Signed-off-by: aszlig <aszlig@nix.build>
Cc: @lovek323, @LnL7, @vaibhavsagar