vim: Import v8.1.0677

* 8.1.0677: look-behind match may use the wrong line number
* 8.1.0676: textprop screendump test fails
* 8.1.0675: text property column in screen columns is not practical
* Update runtime files
* 8.1.0674: leaking memory when updating a single line
* 8.1.0673: functionality for signs is spread out over several files
* 8.1.0672: the Lua interface doesn't know about v:null

gitlog.txt

@@ -1 +1 @@
-* [8.1.0671](https://github.com/vim/vim/releases/tag/v8.1.0671): cursor in the wrong column after auto-formatting\n* [8.1.0670](https://github.com/vim/vim/releases/tag/v8.1.0670): macro for popup menu width is unused\n* [8.1.0669](https://github.com/vim/vim/releases/tag/v8.1.0669): the ex_sign() function is too long\n* [8.1.0668](https://github.com/vim/vim/releases/tag/v8.1.0668): no test for overstrike mode in the command line\n* [8.1.0667](https://github.com/vim/vim/releases/tag/v8.1.0667): textprop test leaves file behind\n* [8.1.0666](https://github.com/vim/vim/releases/tag/v8.1.0666): text property test fails\n* [8.1.0665](https://github.com/vim/vim/releases/tag/v8.1.0665): text property display wrong when 'spell' is set
+* [8.1.0677](https://github.com/vim/vim/releases/tag/v8.1.0677): look-behind match may use the wrong line number\n* [8.1.0676](https://github.com/vim/vim/releases/tag/v8.1.0676): textprop screendump test fails\n* [8.1.0675](https://github.com/vim/vim/releases/tag/v8.1.0675): text property column in screen columns is not practical\n* Update runtime files\n* [8.1.0674](https://github.com/vim/vim/releases/tag/v8.1.0674): leaking memory when updating a single line\n* [8.1.0673](https://github.com/vim/vim/releases/tag/v8.1.0673): functionality for signs is spread out over several files\n* [8.1.0672](https://github.com/vim/vim/releases/tag/v8.1.0672): the Lua interface doesn't know about v:null