Disabled tests which now fail on Windows+mingw4.0 due to GCC 4.8 ABI change (#9205).

These really should have been marked xfail-win32, but that doesn't exist, so xfail-fast it is.

src/test/run-pass/extern-pass-TwoU64s-ref.rs

@@ -9,6 +9,7 @@
 // except according to those terms.
 
 // Test that we ignore modes when calling extern functions.
+// xfail-fast #9205
 
 #[deriving(Eq)]
 struct TwoU64s {

src/test/run-pass/extern-pass-TwoU64s.rs

@@ -14,6 +14,7 @@
 // xfail-fast This works standalone on windows but not with check-fast.
 // possibly because there is another test that uses this extern fn but gives it
 // a different signature
+// xfail-fast #9205
 
 #[deriving(Eq)]
 struct TwoU64s {

src/test/run-pass/extern-return-TwoU64s.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// xfail-fast #9205
+
 struct TwoU64s {
     one: u64, two: u64
 }

src/test/run-pass/struct-return.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// xfail-fast #9205
+
 pub struct Quad { a: u64, b: u64, c: u64, d: u64 }
 pub struct Floats { a: f64, b: u8, c: f64 }