Add naive implementation for ellipse()
Add naive implementation for ellipse()

rust-azure's ellipse() C++ implementation copy/pasted and kind of ported
to Rust. Obviously needs refactor to turn it into idiomatic Rust.

larsbergstrom/servo,splav/servo,notriddle/servo,splav/servo,saneyuki/servo,KiChjang/servo,splav/servo,DominoTree/servo,notriddle/servo,DominoTree/servo,saneyuki/servo,KiChjang/servo,notriddle/servo,KiChjang/servo,saneyuki/servo,notriddle/servo,larsbergstrom/servo,DominoTree/servo,saneyuki/servo,splav/servo,DominoTree/servo,notriddle/servo,notriddle/servo,splav/servo,DominoTree/servo,splav/servo,KiChjang/servo,larsbergstrom/servo,splav/servo,larsbergstrom/servo,larsbergstrom/servo,larsbergstrom/servo,notriddle/servo,larsbergstrom/servo,notriddle/servo,notriddle/servo,DominoTree/servo,notriddle/servo,DominoTree/servo,saneyuki/servo,splav/servo,DominoTree/servo,DominoTree/servo,saneyuki/servo,saneyuki/servo,KiChjang/servo,DominoTree/servo,splav/servo,KiChjang/servo,saneyuki/servo,larsbergstrom/servo,larsbergstrom/servo,splav/servo,KiChjang/servo,KiChjang/servo,KiChjang/servo,KiChjang/servo,saneyuki/servo,larsbergstrom/servo,saneyuki/servo