Add Lanczos & Mitchell resize & rotate modes

I'm trying to achieve the best possible image quality when resizing or rotating images. For most photographic or textural image types, as well as some illustrations or line art, Lanczos (Lanczos3 approximation of Sinc) produces the best quality for scaling up or down, as well as rotation. Mitchell can produce excellent quality with better performance when scaling down, though not necessarily superior to Lanczos, it would still be nice to have this as an option when choosing trade-offs between image quality and performance.

I would like to see Lanczos (specifically Lanczos3) and Mitchell resize and rotate modes added to Jimp.

Existing resize modes of nearest neighbor, bilinear, bicubic, hermite, and bezier are all noticeably lower quality than Lanczos.