patch 9.1.0984: exception handling can be improved

Problem:  exception handling can be improved
Solution: add v:stacktrace and getstacktrace()

closes: #16360

Co-authored-by: Naruhiko Nishino <naru123456789@gmail.com>
Signed-off-by: ichizok <gclient.gaap@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/vim.h b/src/vim.h
index f8090bf..25c9d12 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -2190,7 +2190,8 @@
 #define VV_TYPE_TYPEALIAS 107
 #define VV_TYPE_ENUM	  108
 #define VV_TYPE_ENUMVALUE 109
-#define VV_LEN		110	// number of v: vars
+#define VV_STACKTRACE	110
+#define VV_LEN		111	// number of v: vars
 
 // used for v_number in VAR_BOOL and VAR_SPECIAL
 #define VVAL_FALSE	0L	// VAR_BOOL