Options: Make gnu conform: Make long options start with double-dash

`surelog -help` works, but the more common expected name `surelog --help` does not (this is a [gnu-convention])

Short options should be understood with or without space in the middle.
`surelog -l foo.log` works, but `surelog -lfoo.log` does not.
(this is implemented as an exception for `-I` for instance. But this should always work as expected).

Support long-options with only one dash (e.g. `-help` instead of `--help`) can be tricky of course when we make short-options work without spaces, as it can introduce ambiguities. So if not possible, we can probably even drop it.

[gnu-convention]: https://www.gnu.org/software/libc/manual/html_node/Argument-Syntax.html