Fix compilation issues with clang on POWER

As gcc defaults to -malign-power, removing that option. Also
adding -fno-integrated-as to use GNU assembler for powerpc
assembly optimization files. Fixed other compilation errors
reported in dgemv_t.c file.

ARM64: Add THUNDERX3T110 Target

Move potrf_parallel.c from lapack/getrf to lapack/potrf where it belongs

Fix to store results in correct order for POWER10 GEMM kernels

must have misplaced this in ../getrf when I made that change in March 2018 (40160ff)
the only changes since then were 
RFC : Add half precision gemm for bfloat16 in OpenBLAS Rajalakshmi Srinivasaraghavan
Rajalakshmi Srinivasaraghavan committed on 14 Apr 2020 as 7ebbb50

    Change _STDC_VERSION__ to __STDC_VERSION__ 
Zhiyong Dang committed on 11 May 2018 as 3716267

There is a recent compiler change in __builtin_mma_disassemble_acc() which
affects the order of storing result in POWER10. Also removing new LDFLAG
-mno-power10-stub as it is handled by linker automatically.

WIP Further fixes for 32bit POWER8

Fix alignment errors in the power8 saxpy kernel

Fixes for compilation on POWER with PGI compilers

rebase

Unify BUFFER_SIZE settings for x86_64 again to fix DYNAMIC_ARCH crashes

Patch for building on POWERPC with PGI compilers (was Patch for building on Summit)

Add detection of stdatomic.h for cmake

rebase

Have c_check probe availability of C11 atomics support and stdatomic.h

Update cross-compiling example in README to reflect change in Loongson gcc

for #2723

Handle lack of fortran compiler more gracefully in cmake

Add new linker option for POWER10

While building with DYNAMIC_ARCH on POWER9 with POWER10
aware toolchain, new LDFLAG is needed to avoid POWER10
instructions on PLT calls .