tree+ggc: Change return type of predicate functions from int to bool
Also change internal variable from int to bool.
gcc/ChangeLog:
* tree.h (tree_int_cst_equal): Change return type from int to bool.
(operand_equal_for_phi_arg_p): Ditto.
(tree_map_base_marked_p): Ditto.
* tree.cc (contains_placeholder_p): Update function body
for bool return type.
(type_cache_hasher::equal): Ditto.
(tree_map_base_hash): Change return type
from int to void and adjust function body accordingly.
(tree_int_cst_equal): Ditto.
(operand_equal_for_phi_arg_p): Ditto.
(get_narrower): Change "first" variable to bool.
(cl_option_hasher::equal): Update function body for bool return type.
* ggc.h (ggc_set_mark): Change return type from int to bool.
(ggc_marked_p): Ditto.
* ggc-page.cc (gt_ggc_mx): Change return type
from int to void and adjust function body accordingly.
(ggc_set_mark): Ditto.