If the input JSON to a json function that uses cache comes from an RCStr

value, then use that RCStr value in the parse rather than making a copy.

FossilOrigin-Name: 509ae9c1470dd79d320e84371e1e6662fb85fa0571df5ed8c4d946d10cdfe821

src/sqliteInt.h

@@ -5200,6 +5200,7 @@ void sqlite3FileSuffix3(const char*, char*);
 u8 sqlite3GetBoolean(const char *z,u8);
 
 const void *sqlite3ValueText(sqlite3_value*, u8);
+int sqlite3ValueIsOfClass(const sqlite3_value*, void(*)(void*));
 int sqlite3ValueBytes(sqlite3_value*, u8);
 void sqlite3ValueSetStr(sqlite3_value*, int, const void *,u8,
                         void(*)(void*));