Tech startups will be enthused by the news that Silicon Valley venture capital (VC) veteran General Catalyst is on the verge of raising US$6 billion (£4.8 billion) for backing new companies. It comes hot on the heels of an announcement from Andreessen Horowitz, another major VC, of a new US$7.2 billion investment fund. These are among the largest fundraisings in years, coming at a time when the VC sector has been going through a lull, with…