Pharmacological Characterization of 2NTX-99 [4-Methoxy-N1-(4-trans-nitrooxycyclohexyl)-N3-(3-pyridinylmethyl)-1,3-benzenedicarboxamide], a Potential Antiatherothrombotic Agent with Antithromboxane and Nitric Oxide Donor Activity in Platelet and Vascular Preparations