patch 8.1.1989: the evalfunc.c file is still too big

Problem:    The evalfunc.c file is still too big.
Solution:   Move f_pathshorten() to filepath.c.  Move f_cscope_connection() to
            if_cscope.c.  Move diff_ functions to diff.c.  Move timer_
            functions to ex_cmds2.c.  move callback functions to evalvars.c.
diff --git a/src/proto/ex_cmds2.pro b/src/proto/ex_cmds2.pro
index e0fd3c6..2ecda16 100644
--- a/src/proto/ex_cmds2.pro
+++ b/src/proto/ex_cmds2.pro
@@ -9,6 +9,11 @@
 void add_timer_info_all(typval_T *rettv);
 int set_ref_in_timer(int copyID);
 void timer_free_all(void);
+void f_timer_info(typval_T *argvars, typval_T *rettv);
+void f_timer_pause(typval_T *argvars, typval_T *rettv);
+void f_timer_start(typval_T *argvars, typval_T *rettv);
+void f_timer_stop(typval_T *argvars, typval_T *rettv);
+void f_timer_stopall(typval_T *argvars, typval_T *rettv);
 int autowrite(buf_T *buf, int forceit);
 void autowrite_all(void);
 int check_changed(buf_T *buf, int flags);