patch 8.1.2225: the "last used" info of a buffer is under used

Problem:    The "last used" info of a buffer is under used.
Solution:   Add "lastused" to getbufinfo(). List buffers sorted by last-used
            field. (Andi Massimino, closes #4722)
diff --git a/src/proto/misc1.pro b/src/proto/misc1.pro
index 1a06d7e..2f7bd03 100644
--- a/src/proto/misc1.pro
+++ b/src/proto/misc1.pro
@@ -46,4 +46,5 @@
 char_u *get_isolated_shell_name(void);
 int path_is_url(char_u *p);
 int path_with_url(char_u *fname);
+void add_time(char_u *buf, size_t buflen, time_t tt);
 /* vim: set ft=c : */