due to #1643

I don't have as many benchmarks for these as for gemm, but it should still
make a difference for small matrices.

this required switching to the generic gemm_beta code (which is faster anyway on SKX)
for both DGEMM and SGEMM

Performance for the not-retuned version is in the 30% range

This patch adds the basic infrastructure for adding the SkylakeX (Intel Skylake server)
target. The SkylakeX target will use the AVX512 (AVX512VL level) instruction set,
which brings 2 basic things:
1) 512 bit wide SIMD (2x width of AVX2)
2) 32 SIMD registers (2x the number on AVX2)

This initial patch only contains a trivial transofrmation of the Haswell SGEMM kernel
to AVX512VL; more will follow later but this patch aims to get the infrastructure
in place for this "later".

Full performance tuning has not been done yet; with more registers and wider SIMD
it's in theory possible to retune the kernels but even without that there's an
interesting enough performance increase (30-40% range) with just this change.

Add multithreading support for Haswell DDOT

copied from ashwinyes' implementation in dot_thunderx2t99.c

as the inaccuracies seen in the original testcase for #1332 appear to be due to an artefact that amplifies the very small rounding differences between FMA and discrete multiply+add

The OSX assembler apparently mishandles the argument to decimal .align, leading to a significant loss of performance 
as observed in #730, #901 and most recently #1470

Initialize unitialized values for repeated calls

Address warnings #1357

Tag %1 and %2 as both input and output operands

fix from #1292 extended to the other gemv microkernels

Tag %1 and %2 as both input and output

The inline assembly modifies its input operands, so mark them as output to avoid surprises with optimization. Fixes #1292

related to issue #1332

The testcase from #1332 exposes a problem in daxpy_microk_haswell-2.c that is not seen with
any of the other Intel x86_64 microkernels.

* dead increments in driver/level2

* dead increments in kernel/generic

* part dead increments in kernel/x86_64

Add optimized dsdot to all other x86_64 kernels that use sdot.c

Clean up spurious unused variables in the kernels

TODO: Fix the parser macro to strip trailing whitespaces

remove input from clobbered list