Also select variable when using af on anonymous functions

[arp242]

When using af on an anonymous function that is assigned, such as:

peanuts := func(a string) error {
	return errors.New("I'm alergic!")
}

we will now also select the peanuts variable.

This could be improved by not assuming a single space between = and the
func. Dunno if that's worth the effort ... use gofmt? ;-)

Fixes: #1181

[fatih]

Hi @Carpetsmoker

This seems to be complicated. I've implemented a simpler version: #1345 what do you think? This is configurable, and second it works by using the existing information (only for one liners do we need to calculate the column number of the variable).

[arp242]

Your solution is probably better @fatih. I'll close this. Thanks 👍