sysutils/pftop: add ALTQ option, disable by default

• ALTQ is not in GENERIC and thus browsing through pftop modes the queue view gives an error.
• While there, modernise the ATLQ disable patch, it is not a unified diff.
• Add LICENSE

PR: 215313
Submitted by: Franco Fichtner <franco@opnsense.org>
Approved by: araujo (maintainer)