add includepkgs api

Add api to deal with includepkgs tag:

struct _HySack {
...
Map *includepkgs;		/* list of all whitelisted packages - when
				 * the list is complete it is used to fill
				 * includepkgs and cont_includepkgs variables */
int cont_includepkgs;		/* includepkgs procesed */
Map *fin_includepkgs;		/* pkgs white list (dnf.conf includepkgs option) */
}

/* function adds a packageset pset to includepackgs list to sack.
 * There is necessary to use hy_sack_eval_includepkgs function when
 * includepkgs list is complete to fill fin_includepkgs structure */
void hy_sack_add_includepkgs(HySack sack, HyPackageSet pset);
void hy_sack_set_includepkgs(HySack sack, HyPackageSet pset);
/* fill fin_includepkgs structure by the negation of includepkgs */
void hy_sack_eval_includepkgs(HySack sack);


Signed-off-by: Ivana Hutarova Varekova <varekova@redhat.com>