Auto merge of #2727 - redox-os:redox-0.2.120, r=Amanieu

redox: add siginfo_t and rename sa_handler to sa_sigaction

This improves support for crates like signal_hook_registry

src/unix/redox/mod.rs

@@ -151,12 +151,20 @@ s! {
     }
 
     pub struct sigaction {
-        pub sa_handler: ::sighandler_t,
+        pub sa_sigaction: ::sighandler_t,
         pub sa_flags: ::c_ulong,
         pub sa_restorer: ::Option<extern fn()>,
         pub sa_mask: ::sigset_t,
     }
 
+    pub struct siginfo_t {
+        pub si_signo: ::c_int,
+        pub si_errno: ::c_int,
+        pub si_code: ::c_int,
+        _pad: [::c_int; 29],
+        _align: [usize; 0],
+    }
+
     pub struct sockaddr {
         pub sa_family: ::sa_family_t,
         pub sa_data: [::c_char; 14],