Fix for the very common infinite loop issue, when forgetting to call getIterator

[svermeulen]

I find that when using this library, it is very common to accidentally create infinite loops like this:

for value in lazylualinq.range(1, 10)
   :filter("v % 2 == 0") do
   print(value)
end

Instead of properly doing this:

for value in lazylualinq.range(1, 10)
   :filter("v % 2 == 0")() do
   print(value)
end

I think this is because when the for loop is given a table that has __call metamethod, it assumes it is a normal iterator function, and repeatedly calls it, causing a new iterator function to be created each iteration of the loop. Otherwise it would just produce an error instead of an infinite loop.

For some lua environments an infinite loop is much worse than just triggering an error. We can detect this mistake though, since when lua calls the given iterator function it passes in two parameter values. So we can differentiate between when the lua for-method calls it and when the user calls it themselves.

I am using select() because the parameter values are passed as nil values, so #{...} would return 0

[Henkoglobin]

Huh, interesting find! So the intended way to iterate a sequence would be to pass it to pairs, which would then call the __pairs metamethod and do the right thing from there. I'll admit that I'm basically never using that, though :D

Would you add a unit test for this? Then I'll gladly merge your PR :)