Add a test of multi-in with single-in decoration

[hham]

This PR add a test of AutoFilter with multi-in and single-in to show that a filter with multi-in and single-in is not allowed for now.

[codemercenary]

Thank you, @hham ! This is awesome.

[hham]

Sure.

[jdonald]

So this is still broken on clang, but somehow works with gcc?

If I instantiate [&f_called](float& out) { out = ++f_called; } before the multi-decoration, somehow the test passes.

[codemercenary]

That is very strange indeed, a good finding too--should help me track this one down once I get some time to work on it.

[codemercenary]

@jdonald would you mind merging this one?

[hham]

Works fine on Unit tests on my Mac.

[jdonald]

I double-checked that the test as originally written by Hyoung (floating-point variable and all), now passes on clang.