Emit lifetime end markers for function arguments

Function arguments are (hopefully!) the last places where allocas don't
get proper markers for the end of their lifetimes. This means that this
code using 64 bytes of stack for the function arguments:

````rust
std::io::println("1");
std::io::println("2");
std::io::println("3");
std::io::println("4");
````

But with the proper lifetime markers, the slots can be reused, and
the arguments only need 16 bytes of stack.