Remove qatomic_arch.h

Remove qatomic_arch.h

Make qbasicatomic.h include the OS/compiler/processor dependent
implementation.

For implementations that have not yet been ported to declare a
QAtomicOps, they need to #include <QtCore/qoldbasicatomic.h>, and the
new QBasicAtomicInteger and QBasicAtomicPointer should not be declared.

Change-Id: Ia951834484c9f8dfa75131592e5e716b68ff989b
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>