MFC r338977:

Add description, parameters, options, sysctl and examples of using AQMs to ipfw man page. CoDel, PIE, FQ-CoDel and FQ-PIE AQM for Dummynet exist in FreeBSD 11 and 10.3.

Submitted by: ralsaadi@swin.edu.au
Reviewed by: AllanJude
Differential Revision: https://reviews.freebsd.org/D12507