Fix Win64 ABI conformance when using xmm8-xmm11

Fix Win64 ABI conformance when using xmm8-xmm11

Referring to https://docs.microsoft.com/en-US/cpp/build/stack-usage:

"All memory beyond the current address of RSP is considered volatile:
The OS, or a debugger, may overwrite this memory during a user debug
session, or an interrupt handler.  Thus, RSP must always be set before
attempting to read or write values to a stack frame."

Basically, if-- under extremely rare circumstances-- a context swap were
to occur between saving the values of xmm8-xmm11 and setting the new
value of rsp, the O/S might not preserve that area of the stack.  In
general, libjpeg-turbo should not be using xmm8-xmm11 before or after
the call to jsimd_huff_encode_one_block_sse2(), so this is probably a
non-issue, but it's still a good idea to fix it.

Based on
https://github.com/mayeut/libjpeg-turbo/commit/ff7d2030dd26c7b8c37ff540c594490198843f15