128 bit integers are stable with Rust 1.26

[tirkarthi]

128 bit integers are stable with Rust 1.26 and hence they could be added to the table below :

Length	Signed	Unsigned
8-bit	i8	u8
16-bit	i16	u16
32-bit	i32	u32
64-bit	i64	u64
arch	isize	usize

Ref : https://doc.rust-lang.org/std/u128/index.html
Relevant PR : rust-lang/rust#49101

Relevant section : https://doc.rust-lang.org/book/second-edition/ch03-02-data-types.html#integer-types

Thanks for the book.

[tirkarthi]

Sorry, I just came across #1230 after search. Feel free to close this if it doesn't need to be added.

Thanks

[steveklabnik]

It's actually a duplicate of #1294, though that's a bit hard to tell! Thanks!