Group all X_acquire_release_volatile.h and X_[aligned_]atomic_load_store.h

Group all X_acquire_release_volatile.h and X_[aligned_]atomic_load_store.h
in separate folder

* src/Makefile.am (nobase_private_HEADERS): Update path to
acquire_release_volatile.h, aligned_atomic_load_store.h,
atomic_load_store.h, char_acquire_release_volatile.h,
char_atomic_load_store.h, int_acquire_release_volatile.h,
int_aligned_atomic_load_store.h, int_atomic_load_store.h,
short_acquire_release_volatile.h, short_aligned_atomic_load_store.h,
short_atomic_load_store.h entries (add "loadstore" to prefix).
* src/atomic_ops/sysdeps/all_acquire_release_volatile.h: Likewise.
* src/atomic_ops/sysdeps/all_aligned_atomic_load_store.h: Likewise.
* src/atomic_ops/sysdeps/all_atomic_load_store.h: Likewise.
* src/atomic_ops/sysdeps/gcc/alpha.h: Likewise.
* src/atomic_ops/sysdeps/gcc/mips.h: Likewise.
* src/atomic_ops/sysdeps/hpc/hppa.h: Likewise.
* src/atomic_ops/sysdeps/acquire_release_volatile.h: Move file to
src/atomic_ops/sysdeps/loadstore folder.
* src/atomic_ops/sysdeps/loadstore/aligned_atomic_load_store.h:
Likewise.
* src/atomic_ops/sysdeps/loadstore/atomic_load_store.h: Likewise.
* src/atomic_ops/sysdeps/loadstore/char_acquire_release_volatile.h:
Likewise.
* src/atomic_ops/sysdeps/loadstore/char_atomic_load_store.h: Likewise.
* src/atomic_ops/sysdeps/loadstore/int_acquire_release_volatile.h:
Likewise.
* src/atomic_ops/sysdeps/loadstore/int_aligned_atomic_load_store.h:
Likewise.
* src/atomic_ops/sysdeps/loadstore/int_atomic_load_store.h: Likewise.
* src/atomic_ops/sysdeps/loadstore/short_acquire_release_volatile.h:
Likewise.
* src/atomic_ops/sysdeps/loadstore/short_aligned_atomic_load_store.h:
Likewise.
* src/atomic_ops/sysdeps/loadstore/short_atomic_load_store.h:
Likewise.
* src/atomic_ops/sysdeps/all_acquire_release_volatile.h: Reformat
comment.
* src/atomic_ops/sysdeps/all_aligned_atomic_load_store.h: Likewise.
* src/atomic_ops/sysdeps/all_atomic_load_store.h: Likewise.