It’s not even out yet and some people are predicting “Ghostbusters,’’ the made-in-Massachusetts reboot of the 1984 classic starring Bill Murray, Dan Aykroyd, and Harold Ramis, will be bad. Others, like Aykroyd, are singing its praises. (On Twitter, Aykroyd wrote: “As originator of the original: Saw test screening of new movie. Apart from brilliant, genuine performances from the cast both female and male, it has more laughs and more scares than the first 2 films plus Bill Murray is in it!’’) The movie, which opens here July 15, screened this week in Singapore and fans went nuts. Directed by Paul Feig, “Ghostbusters’’ stars Melissa McCarthy, Kristen Wiig, Kate McKinnon, and Leslie Jones, with cameos by Murray and Sigourney Weaver, among others.