Work around IBM XL C compiler bug

* src/fileio.c (Fcopy_file): Work around a compiler bug in IBM XL
C for AIX, V12.1 (5765-J02, 5725-C72).  Without this patch, the
compiler incorrectly complains “Initialization between types "int"
and "struct timespec" is not allowed” and “Initialization between
types "long" and "struct timespec" is not allowed”.

src/fileio.c

@@ -2386,7 +2386,9 @@ permissions.  */)
 
   if (!NILP (keep_time))
     {
-      struct timespec ts[] = { get_stat_atime (&st), get_stat_mtime (&st) };
+      struct timespec ts[2];
+      ts[0] = get_stat_atime (&st);
+      ts[1] = get_stat_mtime (&st);
       if (futimens (ofd, ts) != 0)
 	xsignal2 (Qfile_date_error,
 		  build_string ("Cannot set file date"), newname);