Honor Single Unix Specification (SUS) by allowing multiple arguments to be grouped behind single `-`

[rootkea]

Hello!

As per SUS Utility syntax guideline 5, command-line utility should allow multiple arguments to be grouped behind single - delimiter.

I have yet to come across the *nix utility which doesn't follow this convention. Can we please honor the Single Unix Specification?

$ chkrootkit -qn
Usage: ./chkrootkit [options] [test ...]
Options:
        -h                show this help and exit
        -V                show version information and exit
        -l                show available tests and exit
        -d                debug
        -q                quiet mode
        -x                expert mode
        -r dir            use dir as the root directory
        -p dir1:dir2:dirN path for the external commands used by chkrootkit
        -n                skip NFS mounted dirs
$ chkrootkit -q -n
<False positives>
$