Previously this returned `int`. Many functions actually take advantage
of the fact this returns exactly 0 or 1. For instance,
`main/streams/xp_socket.c` does:
sockopts |= STREAM_SOCKOP_IPV6_V6ONLY_ENABLED * zend_is_true(tmpzval);
And `Zend/zend_compile.c` does:
child = &ast->child[2 - zend_is_true(zend_ast_get_zval(ast->child[0]))];
I changed a few places trivially from `int` to `bool`, but there are
still many places such as the object handlers which return `int` that
should eventually be `bool`.
c461b60060