* tree-ssa-live.c (set_is_used): Return a bool.
(mark_all_vars_used): Don't take data argument.
(mark_all_vars_used_1): Adjust calls to above, merge handling
of local and global vars.
(remove_unused_scope_block_p): Don't take global_unused_vars,
merge handling of local and global vars.
(remove_unused_locals): Don't allocate/fill/pass global_unused_vars,
use is_used_p for local and global vars.