Fix jenkins build (#6075)
Fix jenkins build (#6075)

underscores in literals are not supported in -source 1.6
https://libgdx.badlogicgames.com/jenkins/job/libgdx/324/console
tommyettinger/libgdx,Zomby2D/libgdx,NathanSweet/libgdx,Zomby2D/libgdx,Zomby2D/libgdx,libgdx/libgdx,stinsonga/libgdx,cypherdare/libgdx,cypherdare/libgdx,Zomby2D/libgdx,bladecoder/libgdx,tommyettinger/libgdx,tommyettinger/libgdx,stinsonga/libgdx,cypherdare/libgdx,NathanSweet/libgdx,cypherdare/libgdx,Zomby2D/libgdx,libgdx/libgdx,tommyettinger/libgdx,libgdx/libgdx,bladecoder/libgdx,cypherdare/libgdx,bladecoder/libgdx,libgdx/libgdx,tommyettinger/libgdx,libgdx/libgdx,bladecoder/libgdx,stinsonga/libgdx,bladecoder/libgdx,NathanSweet/libgdx,stinsonga/libgdx,stinsonga/libgdx,NathanSweet/libgdx,NathanSweet/libgdx