Use generalized load/store if AO_PREFER_GENERALIZED (gcc/generic)

Use generalized load/store if AO_PREFER_GENERALIZED (gcc/generic)

Note: AO_PREFER_GENERALIZED macro is for testing generalize.h mainly.

* src/atomic_ops/sysdeps/gcc/generic-small.template (AO_XSIZE_load,
AO_XSIZE_load_acquire, AO_XSIZE_store, AO_XSIZE_store_release): Do not
define if AO_GCC_HAVE_XSIZE_SYNC_CAS and AO_PREFER_GENERALIZED.
* src/atomic_ops/sysdeps/gcc/generic-small.h: Regenerate.
* src/atomic_ops/sysdeps/gcc/generic.h [AO_HAVE_DOUBLE_PTR_STORAGE]
(AO_GCC_HAVE_double_SYNC_CAS): Move the definition upper to be before
AO_double_load.
* src/atomic_ops/sysdeps/gcc/generic.h [AO_HAVE_DOUBLE_PTR_STORAGE]
(AO_double_load, AO_double_load_acquire, AO_double_store,
AO_double_store_release): Do not define if AO_GCC_HAVE_double_SYNC_CAS
and AO_PREFER_GENERALIZED.