underscore _ ignored output argument. `gettext()` alias

## Description

The symbol named `_` is treated as a special variable used to assign to nothing.

When calling a function or extracting some values, it is sometimes necessary to skip an output argument. If a variable is named `_` the output value will not be assigned.

By default and for compatibility, `_()` is also an alias to gettext().

## Examples

    // only output commands, the 2nd output argument
    [_, commands] = what()

    // multiple list assignment is also supported
    [a, _, _, d] = list(1,2,3,4)(:)

    // this is also available to user-defined functions
    function [a, b, c, d] = myFunc()
      a = 1
      b = 2
      c = 3
      d = 4
    endfunction

    [a, b, _, d] = myFunc()

## See also

- functions
- names
- symbols
- gettext