Failures to obtain or attach shared memory segments would lead to an exit without explanation of the exact cause.
This change introduces a more verbose error message and tries to make the code continue without setting cpu affinity.
Fixes #1351

also replaces one verbatim sched_yield with the YIELDING macro for consistency as suggested in #1351

2D thread distribution for multi-threaded GEMMs

CMake improvements

Allows maximum use of available cores if one of M and N is small and the other is large.

... as the "allocation" code jumped to now does UNLOCK_COMMAND instead of blas_unlock

Make sure that range limit of last thread never exceeds data size

CMake Improvements

Rework __GLIBC_PREREQ checks to avoid breaking non-glibc builds

Fix write past fixed size buffer

Add sched_getcpu implementation for pre-2.6 glibc

Fixes #1210, compilation on RHEL5 with affinity enabled

fixed syrk_thread.c taken from wernsaar

Stride calculation fix copied from https://github.com/wernsaar/OpenBLAS/commit/88900e1

Before this commit, the "position < NUM_BUFFERS" loop condition from
blas_memory_free will be completely optimized away by GCC. This is
because the condition can only be false after undefined behavior has
already been invoked (reading past the end of an array). As a
consequence of this bug, GCC also removes the subsequent if statement
and all the code after the error label because all of it is dead.

This commit switches the loop condition around so it works as intended.

Optimized Implementations for ThunderX2T99