Eliminate C++ warnings about deprecated register keyword (GC source)

Eliminate C++ warnings about deprecated register keyword (GC source)

Issue #206 (bdwgc).

* blacklst.c (GC_number_stack_black_listed, total_stack_black_listed):
Remove register keyword for local variables.
* dyn_load.c [IRIX5 || USE_PROC_FOR_LIBRARIES && !LINUX]
(GC_register_dynamic_libraries): Likewise.
* extra/pcr_interface.c [PCR] (GC_enumerate_block): Likewise.
* finalize.c (GC_grow_table): Likewise.
* headers.c (alloc_hdr, GC_init_headers, GC_remove_counts,
GC_prev_block): Likewise.
* include/private/gc_pmark.h (PUSH_OBJ): Likewise.
* mach_dep.c [!HAVE_PUSH_REGS && !HAVE_BUILTIN_UNWIND_INIT]
(GC_with_callee_saves_pushed): Likewise.
* mark.c (clear_marks_for_block): Likewise.
* mark_rts.c [MSWIN32 || MSWINCE || CYGWIN32] (GC_add_roots_inner):
Likewise.
* mark_rts.c [!NO_DEBUGGING] (GC_is_tmp_root): Likewise.
* os_dep.c [GWW_VDB || MPROTECT_VDB || PROC_VDB || MANUAL_VDB]
(GC_page_was_dirty): Likewise.
* os_dep.c [CHECKSUMS && GWW_VDB || PROC_VDB] (GC_or_pages,
GC_page_was_ever_dirty): Likewise.
* os_dep.c (GC_write_fault_handler): Likewise.
* os_dep.c [PROC_VDB] (GC_read_dirty): Likewise.
* os_dep.c [MPROTECT_VDB && DARWIN] (catch_exception_raise): Likewise.
* os_dep.c [SAVE_CALL_CHAIN && NARGS>0] (GC_save_callers): Likewise.
* pthread_stop_world.c [!NACL] (GC_start_world): Likewise.
* pthread_support.c (GC_delete_thread, GC_delete_gc_thread): Likewise.
* typd_mlc.c (GC_push_complex_descriptor): Likewise.
* win32_threads.c (GC_delete_gc_thread_no_free, GC_delete_thread):
Likewise.