Removed contribTab in PhotonMap and made global variable in pmapcontrib.c as a placeholder for rcontrib's modconttab. rcmain.c sets this pointer to modconttab via a dedicated func initPmapContribTab(). This way the pmapcontrib modules don't need to reference modconttab externally, as this leads to conflicts when linking to rtrace/rpict/rvu; they simply ignore pmapContribTab.