net-p2p/libbt: Update 1.05 -> 1.06

egypcio@googlemail.com takes maintainership

Port changes:

• Add DOCS option
• Add to dependencies
• Port cleanup

PR: 231033
Submitted by: Vinícius Zavam <egypcio@googlemail.com> (original version)
Submitted by: Nathan <ndowens@yahoo.com> (final version)