patch 8.0.0776: function prototypes missing without the quickfix feature

Problem:    Function prototypes missing without the quickfix feature. (Tony
            Mechelynck)
Solution:   Move non-quickfix functions to buffer.c.
diff --git a/src/proto/buffer.pro b/src/proto/buffer.pro
index 183f79a..e9a37de 100644
--- a/src/proto/buffer.pro
+++ b/src/proto/buffer.pro
@@ -53,6 +53,12 @@
 void do_modelines(int flags);
 int read_viminfo_bufferlist(vir_T *virp, int writing);
 void write_viminfo_bufferlist(FILE *fp);
+int bt_quickfix(buf_T *buf);
+int bt_terminal(buf_T *buf);
+int bt_nofile(buf_T *buf);
+int bt_dontwrite(buf_T *buf);
+int bt_dontwrite_msg(buf_T *buf);
+int buf_hide(buf_T *buf);
 char_u *buf_spname(buf_T *buf);
 int find_win_for_buf(buf_T *buf, win_T **wp, tabpage_T **tp);
 void buf_addsign(buf_T *buf, int id, linenr_T lnum, int typenr);