vim-patch:8.0.0420: text garbled when the system encoding differs from 'encoding'

Problem:    When running :make the output may be in the system encoding,
            different from 'encoding'.
Solution:   Add the 'makeencoding' option. (Ken Takata)

2c7292dc5b

src/nvim/buffer.c

@@ -1808,6 +1808,7 @@ void free_buf_options(buf_T *buf, int free_p_ff)
   buf->b_p_ul = NO_LOCAL_UNDOLEVEL;
   clear_string_option(&buf->b_p_lw);
   clear_string_option(&buf->b_p_bkc);
+  clear_string_option(&buf->b_p_menc);
 }