Mark relevant structs with repr(C)

src/libgreen/context.rs

@@ -143,6 +143,7 @@ pub fn swap(out_context: &mut Context, in_context: &Context) {
 // stacks are disabled.
 
 #[cfg(target_arch = "x86")]
+#[repr(C)]
 struct Registers {
     eax: u32, ebx: u32, ecx: u32, edx: u32,
     ebp: u32, esi: u32, edi: u32, esp: u32,

src/libnative/io/c_win32.rs

@@ -20,6 +20,7 @@
 static FD_SETSIZE: uint = 64;
 pub static MSG_DONTWAIT: libc::c_int = 0;
 
+#[repr(C)]
 pub struct WSADATA {
     pub wVersion: libc::WORD,
     pub wHighVersion: libc::WORD,
@@ -32,6 +33,7 @@ pub struct WSADATA {
 
 pub type LPWSADATA = *mut WSADATA;
 
+#[repr(C)]
 pub struct fd_set {
     fd_count: libc::c_uint,
     fd_array: [libc::SOCKET, ..FD_SETSIZE],