Wordpress - How to add "supports" parameter for a Custom Post Type?

Yes, there's a function called add_post_type_support

Hook into init -- late, after the post types have been created -- and add support.

Adding support for excerpts to pages for instance:

<?php
add_action('init', 'wpse70000_add_excerpt', 100);
function wpse70000_add_excerpt()
{
    add_post_type_support('page', 'excerpt');
}

An alternative approach is to hook into register_post_type_args and update the supports array.

This is particularly useful if you have third-party plugins that hook into the CPT arguments to display content.

function wpse70000_add_author_metabox_to_cpt_book( $args, $post_type ) {
    if ($post_type != 'POST_TYPE_NAME') // set post type
        return $args;
    $args['supports'] = array( 'author' ); // set the 'supports' array
    return $args;
}

add_filter( 'register_post_type_args', 'wpse70000_add_author_metabox_to_cpt_book', 10, 2 );