Changes to build on AIX in POWER8 mode

This bug is not there in 8.x nor in the 9.0 daily snapshot.

Fix precompiled kernels on POWER9 and make their use conditional on (old) gcc version

Fix SEGV in cdot_power9

used in KERNEL.POWER9

We were corrupting r2 because the local entry wasn't being
setup correctly.

The ZARCH implementations of ?sum contain a cut & paste-error: An inline
assembly argument is named "sum", but the assembly references "asum"
instead.  The mismatch causes a build error.  This is fixed.

revised fix windows compatible for #2313

Signed-off-by: Wang, Long <long1.wang@intel.com>

Further Power8 big-endian corrections

Signed-off-by: Wang, Long <long1.wang@intel.com>

For large matrix, e.g. M=N=K, and M>1290, int mnk=M*N*K will overflow.
This will lead to wrong branching to single-threading. The performance
is downgraded significantly.

Signed-off-by: Wang, Long <long1.wang@intel.com>

Fix PPC970 big-endian support

The altivec versions of SGEMM and CGEMM fail most test in LAPACK-TESTING when compiled for big endian, STRSM/CTRSM even cause segfaults. The rot kernels either fail the corresponding utest or lead to failures in LAPACK-TESTING.

AVX512 CGEMM & ZGEMM kernels

96-99% 1-thread performance of MKL2018

Optimize SGEMM on SKYLAKEX CPUs

Disable IDAMIN/MAX and IZAMIN/MAX optimizations on big-endian POWER8

90% MKL 1-thread performance.