patch 8.1.1228: not possible to process tags with a function

Problem:    Not possible to process tags with a function.
Solution:   Add tagfunc() (Christian Brabandt, Andy Massimino, closes #4010)
diff --git a/src/vim.h b/src/vim.h
index af779f3..2c9149b 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -1133,19 +1133,20 @@
 /*
  * flags for find_tags().
  */
-#define TAG_HELP	1	/* only search for help tags */
-#define TAG_NAMES	2	/* only return name of tag */
-#define	TAG_REGEXP	4	/* use tag pattern as regexp */
-#define	TAG_NOIC	8	/* don't always ignore case */
+#define TAG_HELP	1	// only search for help tags
+#define TAG_NAMES	2	// only return name of tag
+#define	TAG_REGEXP	4	// use tag pattern as regexp
+#define	TAG_NOIC	8	// don't always ignore case
 #ifdef FEAT_CSCOPE
-# define TAG_CSCOPE	16	/* cscope tag */
+# define TAG_CSCOPE	16	// cscope tag
 #endif
-#define TAG_VERBOSE	32	/* message verbosity */
-#define TAG_INS_COMP	64	/* Currently doing insert completion */
-#define TAG_KEEP_LANG	128	/* keep current language */
+#define TAG_VERBOSE	32	// message verbosity
+#define TAG_INS_COMP	64	// Currently doing insert completion
+#define TAG_KEEP_LANG	128	// keep current language
+#define TAG_NO_TAGFUNC	256	// do not use 'tagfunc'
 
-#define TAG_MANY	300	/* When finding many tags (for completion),
-				   find up to this many tags */
+#define TAG_MANY	300	// When finding many tags (for completion),
+				// find up to this many tags
 
 /*
  * Types of dialogs passed to do_vim_dialog().