Add AVX-512F SIMD support
This adds cpuid detection for AVX-512F and the
low-level SIMD implementation. It is not yet present
in any shipping hardware, but the knights landing
version of Intel MIC will be the first CPU to support
it, as well as future generations of their normal
x86 CPUs (i.e., it merges MIC and x86 SIMD). The
implementation currently only works with icc, and
passes unit tests in the Intel SDE emulator. Some kernel
kernel support functions are not yet implemented, and
the instruction set will not be enabled automatically yet.
Change-Id: I2afa7ac2c1cf29577041c9dfefeb323b86f540c3