Scoped variables in anonymous functions

[VincenzoArceri]

In commit 432526b, support for the anonymous functions has been added. Nevertheless, a bug concerning the scoped variables, when the anonymous function is invoked, is still present.
Let's consider the following function

func main() {
	a := 2
	b := func(f int) int {
			return a * f
		}(5)
}

The current scoping rules hide the variable a to the anonymous function, while it should be visible to it. Currently, when the anonymous function is invoked, any variable visible before the invocation is hidden to it.