Add the SQLITE_SUBTYPE flag, which can be passed to sqlite3_create_function() and similar to indicate to the core that a user function is likely to use sqlite3_result_subtype().

FossilOrigin-Name: 6aa438ce41d460a6782ae63503128b9140c28ff59c2b2eed48b004acf83e0560

src/sqliteInt.h

@@ -1686,6 +1686,7 @@ struct FuncDestructor {
 #define SQLITE_FUNC_WINDOW   0x00010000 /* Built-in window-only function */
 #define SQLITE_FUNC_INTERNAL 0x00040000 /* For use by NestedParse() only */
 #define SQLITE_FUNC_DIRECT   0x00080000 /* Not for use in TRIGGERs or VIEWs */
+#define SQLITE_FUNC_SUBTYPE  0x00100000 /* Result likely to have sub-type */
 
 /*
 ** The following three macros, FUNCTION(), LIKEFUNC() and AGGREGATE() are
@@ -3611,6 +3612,7 @@ struct Window {
   int regOne;             /* Register containing constant value 1 */
   int regStartRowid;
   int regEndRowid;
+  u8 bExprArgs;
 };
 
 #ifndef SQLITE_OMIT_WINDOWFUNC