auto merge of #10064 : luqmana/rust/vvv, r=nikomatsakis

Fixes #2057.

Example:
```Rust
#[no_std];

type c_char = u8;
type c_int = i32;
type size_t = uint;

extern {
    fn printf(format: *c_char, ...) -> c_int;
}

#[lang="fail_bounds_check"]
fn fail_bounds_check(_: *c_char, _: size_t, _: size_t, _: size_t) {}

#[start]
#[fixed_stack_segment]
fn main(_: int, _: **u8) -> int {
    unsafe {
        let msg = bytes!("Hello World!

1 files changed, 3 insertions, 0 deletions

diff --git a/src/libstd/unstable/intrinsics.rs b/src/libstd/unstable/intrinsics.rs
index d042440b4f3..404ed85985c 100644
--- a/src/libstd/unstable/intrinsics.rs
+++ b/src/libstd/unstable/intrinsics.rs
@@ -160,7 +160,10 @@ pub trait TyVisitor {
     fn visit_enter_fn(&mut self, purity: uint, proto: uint,
                       n_inputs: uint, retstyle: uint) -> bool;
     fn visit_fn_input(&mut self, i: uint, mode: uint, inner: *TyDesc) -> bool;
+    #[cfg(stage0)]
     fn visit_fn_output(&mut self, retstyle: uint, inner: *TyDesc) -> bool;
+    #[cfg(not(stage0))]
+    fn visit_fn_output(&mut self, retstyle: uint, variadic: bool, inner: *TyDesc) -> bool;
     fn visit_leave_fn(&mut self, purity: uint, proto: uint,
                       n_inputs: uint, retstyle: uint) -> bool;