SACRAMENTO - High gas prices are doing more than causing motorists grief -- they are generating a windfall for California's treasury and triggering a battle over how to spend it. At stake is $1.5 billion from sales taxes on gasoline that voters said in 2002 they want directed to roads, trains and buses. Gov. Arnold Schwarzenegger and the Legislature used the money this year to balance the budget instead. Meanwhile, the run-up in prices at the pump is fattening the pot. California stands to earn $358 million more from sales taxes on gas in 2004 than it did the year...