Performance: Use nvim_buf_set_lines for neovim

`setline()` gets called for every item on the array,
this results on the neovim buffer callbacks to be called
`n` times, using `nvim_buf_set_lines()` makes this change in just one
call

Author: stsewd

autoload/rustfmt.vim

@@ -157,7 +157,14 @@ function! s:RunRustfmt(command, tmpname, from_writepre)
         endif
 
         call s:DeleteLines(len(l:content), line('$'))
-        call setline(1, l:content)
+        if has('nvim') && exists('*nvim_buf_set_lines')
+            " setline() gets called for every item on the array,
+            " this results on the neovim buffer callbacks being called n times,
+            " using nvim_buf_set_lines() makes the change in one call.
+            call nvim_buf_set_lines(0, 0, -1, v:true, l:content)
+        else
+            call setline(1, l:content)
+        endif
 
         " only clear location list if it was previously filled to prevent
         " clobbering other additions