NEW DELHI — It may be better known for saccharine Bollywood love songs and Hindu devotional tunes, but India has an enduring love for rock-metal acts that have fallen off the radar in the US — if they're even still alive. For college graduates from 22 to 45 years old, forgotten bands like Deep Purple, Dire Straits and, yes, Iron Maiden remain immortal — thanks largely to the country's legion of engineers.