Xcode: add guiradialslider.* to project

VDrift/vdrift@d245981
Xcode: remove hud*.* and inputgraph.h from project

VDrift/vdrift@32ac4dc
Dependencies: update cURL to 7.39.0
Dependencies: update WebP to 0.4.2
Merge branch 'hud'
Dependencies: update Boost to 1.57.0