vim-patch:8.1.0014: qf_init_ext() is too long

Problem:    qf_init_ext() is too long.
Solution:   Split it into multiple functions. (Yegappan Lakshmanan,
            closes vim/vim#2939)
6053f2d29a

src/nvim/memline.c

@@ -1929,6 +1929,7 @@ int ml_append_buf(
     colnr_T len,                    // length of new line, including NUL, or 0
     bool newfile                    // flag, see above
 )
+  FUNC_ATTR_NONNULL_ARG(1)
 {
   if (buf->b_ml.ml_mfp == NULL)
     return FAIL;