patch 8.1.2331: the option.c file is still very big

Problem:    The option.c file is still very big.
Solution:   Move a few functions to where they fit better. (Yegappan
            Lakshmanan, closes #4895)
diff --git a/src/proto/change.pro b/src/proto/change.pro
index c31c442..badb19d 100644
--- a/src/proto/change.pro
+++ b/src/proto/change.pro
@@ -15,6 +15,8 @@
 void deleted_lines_mark(linenr_T lnum, long count);
 void changed_lines(linenr_T lnum, colnr_T col, linenr_T lnume, long xtra);
 void unchanged(buf_T *buf, int ff, int always_inc_changedtick);
+void save_file_ff(buf_T *buf);
+int file_ff_differs(buf_T *buf, int ignore_empty);
 void ins_bytes(char_u *p);
 void ins_bytes_len(char_u *p, int len);
 void ins_char(int c);