patch 8.0.1817: a timer may change v:count unexpectedly

Problem:    A timer may change v:count unexpectedly.
Solution:   Save and restore v:count and similar variables when a timer
            callback is invoked. (closes #2897)
diff --git a/src/proto/eval.pro b/src/proto/eval.pro
index 3bbe815..a096156 100644
--- a/src/proto/eval.pro
+++ b/src/proto/eval.pro
@@ -67,6 +67,8 @@
 dict_T *get_vim_var_dict(int idx);
 void set_vim_var_char(int c);
 void set_vcount(long count, long count1, int set_prevcount);
+void save_vimvars(vimvars_save_T *vvsave);
+void restore_vimvars(vimvars_save_T *vvsave);
 void set_vim_var_string(int idx, char_u *val, int len);
 void set_vim_var_list(int idx, list_T *val);
 void set_vim_var_dict(int idx, dict_T *val);