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/evalfunc.c b/src/evalfunc.c
index 3028cf9..9720691 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -2007,6 +2007,8 @@
 			ret_void,	    f_feedkeys},
     {"file_readable",	1, 1, FEARG_1,	    arg1_string,	// obsolete
 			ret_number_bool,    f_filereadable},
+    {"filecopy",	2, 2, FEARG_1,	    arg2_string,
+			ret_number_bool,    f_filecopy},
     {"filereadable",	1, 1, FEARG_1,	    arg1_string,
 			ret_number_bool,    f_filereadable},
     {"filewritable",	1, 1, FEARG_1,	    arg1_string,