patch 8.2.2728: special key names don't work if 'isident' is cleared

Problem:    Special key names don't work if 'isident' is cleared.
Solution:   Add vim_isNormalIDc() and use it for special key names.
            (closes #2389)
diff --git a/src/version.c b/src/version.c
index 0abdbe5..f041987 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2728,
+/**/
     2727,
 /**/
     2726,