Refactored FlxObject::preUpdate() to remove uneccessary code

[IQAndreas]

• Combined two if statements (one of them unnecessary)
• Replaced an unecessary a=a-b with a-=b

[moly]

I'm happy with this.

[Dovyski]

Much better :)

[IQAndreas]

A worker at GitHub just showed me a nice way of making that ugly diff much clearer. If you append ?w=1 to the URL, the diff ignores whitespace.

Before
After

Now you can clearly see what I was actually changing. :)