Brought LDC up to be competitive with GCC and Clang, with GDC close behind. For speed, immutable-ise everything, use @trusted over @safe and use core.stdc for some maths functions
Changed get_coordinates to return Vec2[8] instead of writing and immediately reading from N2DContext.origins/gradients. Now on par with Rust
Added SSE flags for GDC
Removed unnecessary import to std.typecons
Update benchmark numbers and compiler versions.