Move definitions of ordered loads/stores to inner separate headers

Move definitions of ordered loads/stores to inner separate headers
(code refactoring)

* src/Makefile.am (nobase_private_HEADERS): Add ordered_loads_only.h,
ordered_stores_only.h entries.
* src/atomic_ops/sysdeps/loadstore/ordered_loads_only.h: New file.
* src/atomic_ops/sysdeps/loadstore/ordered_stores_only.h: Likewise.
* src/atomic_ops/sysdeps/ordered_except_wr.h: Include
ordered_stores_only.h.
* src/atomic_ops/sysdeps/ordered_except_wr.h (AO_store_write,
AO_store_release, AO_char_store_write, AO_char_store_release,
AO_short_store_write, AO_short_store_release, AO_int_store_write,
AO_int_store_release): Move to ordered_stores_only.h (with the
corresponding AO_HAVE_x macros).
* src/atomic_ops/sysdeps/read_ordered.h: Include ordered_loads_only.h.
* src/atomic_ops/sysdeps/read_ordered.h (AO_load_read,
AO_load_acquire, AO_char_load_read, AO_char_load_acquire,
AO_short_load_read, AO_short_load_acquire, AO_int_load_read,
AO_int_load_acquire): Move to ordered_loads_only.h (with the
corresponding AO_HAVE_x macros).