Type-parameterized main breaks trans

```
fn main<T>() { }
```

Assertion failed: ((Args.size() == FTy->getNumParams() || (FTy->isVarArg() && Args.size() > FTy->getNumParams())) && "Calling a function with bad signature!"), function init, file /Users/jruderman/code/rust/src/llvm/lib/VMCore/Instructions.cpp, line 269.

For comparison, adding an argument to main gives "wrong type in main function".
