Code refactoring of specific.c and specific.h;

Code refactoring of specific.c and specific.h;
cast pointers to word instead of unsigned long

* include/private/specific.h (CACHE_HASH, HASH): Add parentheses
around the argument.
* include/private/specific.h (CACHE_HASH): Remove unnecessary cast to
long.
* include/private/specific.h (HASH): Rename "n" argument to "p";
cast "p" to word instead of long; cast result to unsigned.
* include/private/specific.h (quick_thread_id, INVALID_QTID): Cast to
word instead of unsigned long.
* specific.c (GC_key_create_inner): Cast invalid_tse.next (pointer) to
word instead of unsigned long.
* include/private/specific.h (GC_slow_getspecific, GC_getspecific):
Change type of "qtid" from unsigned long to word.
* specific.c (GC_slow_getspecific): Likewise.
* include/private/specific.h (GC_getspecific): Remove "hash_val"
local variable.
* specific.c: Do not include gc_priv.h as included from
thread_local_alloc.h; do not include atomic_ops.h as included from
specific.h file.