Add Collections#synchronizedSet
Add Collections#synchronizedSet

Signed-off-by: Johannes Schindelin <53fb8db7833fca1e1746dd8592f61048d350f64c@gmx.de>

lostdj/avian,getlantern/avian,bigfatbrowncat/avian-pack.avian,getlantern/avian,dicej/avian,joshuawarner32/avian,bgould/avian,MaartenR/avian,joshuawarner32/avian,bgould/avian,ucdseniordesign/avian,minor-jason/avian,joshuawarner32/avian,dicej/avian,minor-jason/avian,bigfatbrowncat/avian-pack.avian,lostdj/avian,minor-jason/avian,MaartenR/avian,lwahlmeier/avian,joshuawarner32/avian,lwahlmeier/avian,dicej/avian,lwahlmeier/avian,bigfatbrowncat/avian-pack.avian,bigfatbrowncat/avian-pack.avian,marcinolawski/avian,marcinolawski/avian,ucdseniordesign/avian,lwahlmeier/avian,lostdj/avian,minor-jason/avian,MaartenR/avian,bgould/avian,bgould/avian,getlantern/avian,dicej/avian,lostdj/avian,MaartenR/avian,marcinolawski/avian,ucdseniordesign/avian,marcinolawski/avian,getlantern/avian,ucdseniordesign/avian