Regarding the deprecated constructor you can fix that by opening file qa-plugin/google-cse/qa-google-cse.php. That file has a class name on top. There will be a function (most likely on line 24) that will have the same class name. You have to change the name of the function so that it becomes __constructor (note there are 2 underscores).
For example, if the class looks like this:
class qa_googlecse {
public qa_googlecse() {
...
}
}
You have to change it into
class qa_googlecse {
public function __constructor() {
...
}
}
Regarding the second issue it doesn't seem to be a bug in the core. A plugin must be messing things up or you made a core hack that broke something. You could try removing the core hacks and plugins one by one and see which one is the one to blame.