/// convert byte to string with copying value.
///
/// # Examples
///
/// ```
/// extern crate drumatech;
/// use drumatech::conv;
/// let c : u8 = 0x41;
/// let s : String = conv::u8_give_string(c);
/// assert_eq!(String::from("A"),s);
/// ```
/// convert byte to string that giving mutable reference to func.
///
/// # Examples
///
/// ```
/// extern crate drumatech;
/// use drumatech::conv;
/// let mut c : u8 = 0x41;
/// let s : String = conv::u8_to_string(&mut c);
/// assert_eq!(String::from("A"),s);
/// ```