Blender Git Loki

GWN: Element Buffer: Refactor / Optimisation.

- Upload the data to the GPU directly when creating the element buffer in
GWN_indexbuf_build_in_place().

- Convert data in place when squeezing the indices and removing the need
for another allocation.

- GWN_indexbuf_build_in_place() can be used with already used element
buffers and reupload their data without changing vbo id (keeping vaos
up to date).