Structural studies on polynuclear osmium carbonyl hydrides. 16. Crystal structure of (.mu.-H)(.mu.-OMe)Os3(CO)10 and a comparison of the hinged Os(.mu.-H)2Os, Os(.mu.-H)(.mu.-OMe)Os, and Os(.mu.-OMe)2Os bridges in trinuclear (.mu.-H)n(.mu.-OMe)2-nOs3(CO)10 (n = 0-2) complexes