Use vis meta-variable is macros

[ratijas]

Declarative macros like the one below could use the relatively new visibility aka :vis macro meta-variable instead of manual pub($tt*) etc. It had some issues in past, but now it's mostly fixed and safe to use.

rust-cpp/cpp/src/lib.rs

Lines 348 to 358 in 46c1f8d

	macro_rules! cpp_class {
	($(#[$($attrs:tt)*])* unsafe struct $name:ident as $type:expr) => {
	$crate::__cpp_class_internal!{@parse [ $(#[$($attrs)*])* ] [] [unsafe struct $name as $type] }
	};
	($(#[$($attrs:tt)*])* pub unsafe struct $name:ident as $type:expr) => {
	$crate::__cpp_class_internal!{@parse [ $(#[$($attrs)*])* ] [pub] [unsafe struct $name as $type] }
	};
	($(#[$($attrs:tt)*])* pub($($pub:tt)*) unsafe struct $name:ident as $type:expr) => {
	$crate::__cpp_class_internal!{@parse [ $(#[$($attrs)*])* ] [pub($($pub)*)] [unsafe struct $name as $type] }
	};
	}