vim: Import v8.1.0682

* 8.1.0682: text properties not adjusted when backspacing replaced text
* 8.1.0681: text properties as not adjusted for deleted text
* 8.1.0680: not easy to see what features are unavailable
* 8.1.0679: sign functions do not take buffer argument as documented
* 8.1.0678: text properties as not adjusted for inserted text

gitlog.txt

@@ -1 +1 @@
-* [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
+* [8.1.0682](https://github.com/vim/vim/releases/tag/v8.1.0682): text properties not adjusted when backspacing replaced text\n* [8.1.0681](https://github.com/vim/vim/releases/tag/v8.1.0681): text properties as not adjusted for deleted text\n* [8.1.0680](https://github.com/vim/vim/releases/tag/v8.1.0680): not easy to see what features are unavailable\n* [8.1.0679](https://github.com/vim/vim/releases/tag/v8.1.0679): sign functions do not take buffer argument as documented\n* [8.1.0678](https://github.com/vim/vim/releases/tag/v8.1.0678): text properties as not adjusted for inserted text