* Add multithreading support

copied from the ThunderX2T99 kernel. For #2221

Remove case-sensitivity in x86 LSAME on (AMD) cpus without CMOV

Problem was already noticed some years ago in #238, but back then the problem was only corrected in one of the #ifdef branches.
Fixes #2214

Replace vpermpd with vpermilpd in the Haswell DTRMM kernel

Replace most vpermpd calls in the Haswell DTRSM_RN kernel

to improve performance on AMD Zen (#2180) applying wjc404's improvement of the DGEMM kernel from #2186

Add vbroadcastsd kernel to dgemm_kernel_4x8_haswell.S

Replace vpermpd with vpermilpd in the Haswell/Zen zdot microkernel

to improve performance on Zen/Zen2 (as demonstrated by wjc404 in #2180)

replaced a bunch of vpermpd instructions with vpermilpd and vperm2f128

power9 cgemm/ctrmm. new sgemm 8x16

Signed-off-by: Piotr Kubaj <pkubaj@anongoth.pl>

improved power9 zgemm,sgemm

As noted in #1912 and comment on #1942, the combined implementation happens to "do the right thing" on hardfp, but cannot return both value and index on softfp where they would have to share the return register

* Mark iamax_sse.S as unsuitable for MIN due to issue #2116
* Use iamax.S rather than iamax_sse.S for ISMIN/ISAMIN on all x86_64 as workaround for #2116

Disable the SkyLakeX DGEMMIxCOPY kernels as well

#1955

as a stopgap measure for https://github.com/numpy/numpy/issues/13401 as mentioned in #1955

sgemm/strmm kernel for power9

Add (C)BLAS extension ?sum