Some Linux distributions (notably SuSE) have raised CPU_SETSIZE to 4096, apparently disregarding API limitations.
From #1348, the highest value to survive array initialization (on a desktop system) is 3232, and 1024 - which is the 
more usual CPU_SETSIZE limit, was demonstrated to work fine on an actual bignuma system.

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

CMake improvements

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

CMake Improvements

Add sched_getcpu implementation for pre-2.6 glibc

Fixes #1210, compilation on RHEL5 with affinity enabled

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

Add new targets for ARM64

Ref. #995, may possibly help solve issues seen in 660,883