Attempt to rebase #526 with current main

Hand-merged #526 into current main code

Some basic examples compile, but `reflect.h2` doesn't yet, needs investigation

I've commented out some error message emission on what appeared to be trial parses(?), because the presence of the error message stopped further processing

Author: hsutter

include/cpp2util.h

@@ -368,6 +368,17 @@ using _schar     = signed char;      // normally use i8 instead
 using _uchar     = unsigned char;    // normally use u8 instead
 
 
+//-----------------------------------------------------------------------
+//
+//  fn_t<R(ArgTypes...)>       For emitted Cpp2 function types
+//
+//-----------------------------------------------------------------------
+//
+template<typename T>
+    requires std::is_function_v<T>
+using fn_t = T;
+
+
 //-----------------------------------------------------------------------
 //
 //  String utilities