Use ‘const’ to clarify GC marking
Add ‘const’ to make the GC marking code a bit clearer. This can also help the compiler in some cases, I think because GCC can now determine more often that the value of a static C variable can be cached when its address is now converted to ‘Lisp Object const *’ before escaping. * src/alloc.c (staticvec, mark_maybe_objects, mark_memory) (mark_stack, staticpro, mark_object_root_visitor) (garbage_collect_1): * src/pdumper.c (dump_ptr_referrer, dump_emacs_reloc_to_lv) (dump_emacs_reloc_to_emacs_ptr_raw, dump_root_visitor): * src/lisp.h (vcopy, struct gc_root_visitor): * src/sysdep.c (stack_overflow): * src/thread.c (mark_one_thread): * src/thread.h (struct thread_state): Use pointer-to-const instead of plain pointer in some GC-related places where either will do.