patch 9.1.0465: missing filecopy() function

Problem:  missing filecopy() function
Solution: implement filecopy() Vim script function
          (Shougo Matsushita)

closes: #12346

Co-authored-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Shougo Matsushita <Shougo.Matsu@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/proto/fileio.pro b/src/proto/fileio.pro
index 3f7b30d..8d97870 100644
--- a/src/proto/fileio.pro
+++ b/src/proto/fileio.pro
@@ -26,6 +26,7 @@
 char_u *buf_modname(int shortname, char_u *fname, char_u *ext, int prepend_dot);
 int vim_fgets(char_u *buf, int size, FILE *fp);
 int vim_rename(char_u *from, char_u *to);
+int vim_copyfile(char_u *from, char_u *to);
 int check_timestamps(int focus);
 int buf_check_timestamp(buf_T *buf, int focus);
 void buf_reload(buf_T *buf, int orig_mode, int reload_options);
diff --git a/src/proto/filepath.pro b/src/proto/filepath.pro
index 53fa4ec..46f51cb 100644
--- a/src/proto/filepath.pro
+++ b/src/proto/filepath.pro
@@ -6,6 +6,7 @@
 void f_delete(typval_T *argvars, typval_T *rettv);
 void f_executable(typval_T *argvars, typval_T *rettv);
 void f_exepath(typval_T *argvars, typval_T *rettv);
+void f_filecopy(typval_T *argvars, typval_T *rettv);
 void f_filereadable(typval_T *argvars, typval_T *rettv);
 void f_filewritable(typval_T *argvars, typval_T *rettv);
 void f_finddir(typval_T *argvars, typval_T *rettv);