Macro impl_u8_enum

macro_rules! impl_u8_enum {
    ($Enum: ident; $($Variant: ident $(,)?)*) => { ... };
    ($Enum: ident; $($Variant: ident = $val: expr $(,)?)*) => { ... };
    ($Enum: ident; $size: tt; $($Variant: ident = $val: expr $(,)?)*) => { ... };
}