Fixed single-click

[blockchainian]

this pr fixes left click so that it opens/closes the folding.

[raven42]

I believe the original intent of the feature was only to allow folding when the open/close character is clicked. It looks like with this change, that is being expanded to open/close the fold if the click occurs anywhere on the line. Am I interpreting that correctly? I think I'm ok with that change, but it would need to be updated to account for nested folds.

If we take a python script like this:

def my_func():
    print("first layer")

    def inner_func():
        print("second layer")

        def inner_inner_func():
            print("third layer")
        print("went back to the second layer")
    print("went back to the first layer")

Then the fold open/close doesn't work for the internal definition of inner_func().

If you can make it work to so this type of definition works as well, then I would be ok merging in this change.