No one in the mile-high Nepalese capital of Katmandu has ever forgotten the lavish coronation of bean-shaped King Mahendra in 1956, when the tiny Himalayan country imported 40 taxicabs, 130 Indian waiters, and everything from pastel bathtubs to Coca-Cola. Now the Nepalese are at it again, this time with a well-publicized royal wedding, billed as one of the most lavish Hindu nuptial ceremonies in history.     Hiding the Hippies. The wedding bill came to $9.5 million—no mean effort for a country whose 10 million people get by on a yearly per capita income of $77. In Katmandu, roads were widened and repaved, street lamps were installed, and Nepalese workmen painted over everything in sight, including the bronze statues of the Rana prime ministers. A new $2 million royal palace was rushed to completion to dazzle an anticipated crush of 3,000 foreign guests. The Nepalese cleared out the shaggiest of the Western hippies, who come to Katmandu to get high on the altitude and cheap hash, and they brought in more than 100 German and Japanese cars to handle the guests. Government offices were cleared from the old 1,200-room Palace of the Lion to make room for the bride's sizable family.     Though more than 50 heads of state were invited, only a few, including Laos' King Savang Vat-thana made it in person. Despite efforts by U.S. Ambassador Carol Laise to snare Tricia Nixon, Ohio Senator William Saxbe was the U.S. representative.