The file lib/atomic.h is the only machine-dependent file in the test suite
that breaks compilation of the test static/session01 on ARM.

The file is moved into a separate directory and the build system is modified
accordingly to prevent this.
Signed-off-by: Alexander Kartashov <alekskartashov@parallels.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>