Improvements to numeric literals (underscores, hex, octal, binary)

[martint]

As specified in SQL 2023:

<unsigned integer> ::=
    <unsigned decimal integer>
  | <unsigned hexadecimal integer>
  | <unsigned octal integer>
  | <unsigned binary integer>

<unsigned decimal integer> ::=
  <digit> [ { [ <underscore> ] <digit> }... ]

<unsigned hexadecimal integer> ::=
  0X { [ <underscore> ] <hexit> }...

<unsigned octal integer> ::=
  0O { [ <underscore> ] <octal digit> }...

<unsigned binary integer> ::=
  0B { [ <underscore> ] <binary digit> }...

Release notes

(x) Release notes are required, with the following suggested text:

# General
* Add support for underscores in numeric literals.
* Add support for hexadecimal, binary, and octal numeric literals.

[dain]

BTW, in general this syntax is dangerous because parse long supports a leading sign. It isn't a problem here because the grammar doesn't allow that, but I ran into code in Hive that did this and ended up supporting 0x-123

[mosabua]

@nineinchnick and @mosabua are working on docs for this.