Blender Git Loki

Use advantage of SSE2 instructions in gaussian blur node

This gives around 30% of speedup for gaussian blur node.

Pretty much straightforward implementation inside the node
itself, but needed to implement some additional things:

- Aligned malloc. It's needed to load data onto SSE registers
faster. based on the aligned_malloc() from Libmv with
some additional trickery going on to support arbitrary
alignment (this magic is needed because of MemHead).

In the practice only 16bit alignment is supported because
of the lack of aligned malloc with arbitrary alignment
for OSX. Not a bit deal for now because we need 16 bytes
alignment at this moment only. Could be tweaked further
later.

- Memory buffers in compositor are now aligned to 16 bytes.
Should be harmless for non-SSE cases too. just mentioning.

Reviewers: campbellbarton, lukastoenne, jbakker

Reviewed By: campbellbarton

CC: lockal

Differential Revision: https://developer.blender.org/D564