Add Result<(), error_enum> enum binding

For enums representing errors, often the Ok variant is the 0 value of the enum. It would be convenient if bindgen could replace this enum with a Result on the Rust side.

Example C-enum:

enum MY_C_ERRORCODE {
   MY_C_ERRORCODE_SUCCESS,
   MY_C_ERRORCODE_ERROR1,
   MY_C_ERRORCODE_ERROR2,
}

Expected Rust binding:

#[repr(transparent)]
pub struct MY_C_ERRORCODE_NZ(NonZero<c_int>);

impl MY_C_ERRORCODE {
    pub const ERROR1 = MY_C_ERRORCODE_NZ(NonZero::new(1).unwrap()));
    pub const ERROR2 = MY_C_ERRORCODE_NZ(NonZero::new(2).unwrap()))
}

// Perhaps this typedef could be omitted, and usages in the API could just use the result directly
type MY_C_ERRORCODE = Result<(), MY_C_ERRORCODE_NZ>;

This should work well at least when assuming that the generated non-zero enum representation is Newtype based.