Add binary literal

[privat]

Add binary literal syntax, e.g. 0b101010.

Decimal, hexadecimal, and octal are already handled, but binary was missing. Binary literals are useful for testing flags and to teach binary to students.

This is consistent with the GNU assembler syntax that accept it https://sourceware.org/binutils/docs-2.40/as/Integers.html

Add also some simple tests on integer literals.