vim-patch:7.4.2018

Problem:  buf_valid() can be slow when there are many buffers.
Solution: Add bufref_valid(), only go through the buffer list
          when a buffer was freed.

b25f9a97e9

src/nvim/version.c

@@ -422,7 +422,7 @@ static int included_patches[] = {
   // 2021,
   // 2020 NA
   2019,
-  // 2018,
+  2018,
   2017,
   // 2016 NA
   2015,