Local goto labels
=================

This can be used to provide scope for goto labels and avoid accidentally
jumping to an unrelated block.

Syntax idea (borrowed from the GCC extension):

    func f()
    {
        {
            label skip
            ...
            goto skip
            ...
          skip:
            ...
        }
        {
            label skip
            ...
            goto skip
            ...
          skip:
            ...
        }
    }