[lightbeam] float stack arguments

[sunfishcode]

#803 updated to the latest spec_testsuite, which contained a new test which triggers an assertion failure with in lightbeam in call.wast.

The assertion failure is "Float args on stack not yet supported". The testcase does this:

  (func $return-from-long-argument-list-helper (param f32 i32 i32 f64 f32 f32 f32 f64 f32 i32 i32 f32 f64 i64 i64 i32 i64 i64 f32 i64 i64 i64 i32 f32 f32 f32 f64 f32 i32 i64 f32 f64 f64 f32 i32 f32 f32 f64 i64 f64 i32 i64 f32 f64 i32 i32 i32 i64 f64 i32 i64 i64 f64 f64 f64 f64 f64 f64 i32 f32 f64 f64 i32 i64 f32 f32 f32 i32 f64 f64 f64 f64 f64 f32 i64 i64 i32 i32 i32 f32 f64 i32 i64 f32 f32 f32 i32 i32 f32 f64 i64 f32 f64 f32 f32 f32 i32 f32 i64 i32) (result i32)
    (local.get 99)
  )

[alexcrichton]

Lightbeam was removed in #3390 as explained in RFC 14, so I'm going to close this.