(Adds Venezuela government comments) RIYADH, Jan 11 (Reuters) - Venezuelan President Nicolas Maduro met Saudi Arabia's Crown Prince Salman in Riyadh on Sunday as part of a diplomatic tour of OPEC members to discuss falling oil prices, which have hit its eco**my hard. The Saudi side in the meeting included Oil Minister Ali al-Naimi and several princes including Deputy Crown Prince Muqrin, intelligence chief Prince Khaled bin Bandar and three sons of King Abdullah, who is in hospital, state media reported. ...