Clean up docs for macros

[jasongrlicky]

We can use the following pattern to hide details that we don't want to be documented:

#[macro_export]
macro_rules! macro_external {
    ($($params:tt)+) => {
       macro_ internal!($($params)+)
    };
}

#[macro_export]
#[doc(hidden)]
macro_rules! macro_internal {
   // ...
}