patch 8.1.1385: signed/unsigned compiler warning

Problem:    Signed/unsigned compiler warning.
Solution:   Use STRLEN() instead of strlen().

src/fileio.c

@@ -7198,7 +7198,7 @@ readdir_core(
     if (buf == NULL)
 	return FAIL;
     STRNCPY(buf, path, MAXPATHL-5);
-    p = buf + strlen(buf);
+    p = buf + STRLEN(buf);
     MB_PTR_BACK(buf, p);
     if (*p == '\\' || *p == '/')
 	*p = NUL;

src/version.c

@@ -767,6 +767,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1385,
 /**/
     1384,
 /**/