Add geom_util.{h,m}

Provides hydra_push/to_ns{rect,point,size} functions.
Add geom_util.{h,m} to project.
Use geom_util functions in geometry.m.
Use geom_util functions in mouse.m
Use geom_util functions in screen.m
Use geom_util functions in textgrid.m
Use geom_util functions in window.m