Removes the union in unix/tls.h to separate os_seg_info from client slots. As a result, client slots are correctly initialised to zero as specified in the docs.
Adds a regression test to ensure slots are initialised correctly.
Issue: #3990
Removes the union in unix/tls.h to separate os_seg_info from client slots. As a result, client slots are correctly initialised to zero as specified in the docs.
Adds a regression test to ensure slots are initialised correctly.
Issue: #3990