vim-patch:8.1.0270: checking for a Tab in a line could be faster

Problem:    Checking for a Tab in a line could be faster.
Solution:   Use strchr() instead of strrchr(). (closes vim/vim#3312)
b31a3acce1

src/nvim/ex_cmds.c

@@ -335,7 +335,7 @@ static int linelen(int *has_tab)
   len = linetabsize(line);
   // Check for embedded TAB.
   if (has_tab != NULL) {
-    *has_tab = STRRCHR(first, TAB) != NULL;
+    *has_tab = vim_strchr(first, TAB) != NULL;
   }
   *last = save;