Auto merge of #1329 - alex:patch-1, r=gnzlbg

Deprecate _pad field on siginfo_t

As discussed in #1316

Author: bors

src/unix/notbsd/linux/other/mod.rs

@@ -48,6 +48,12 @@ s! {
         pub si_signo: ::c_int,
         pub si_errno: ::c_int,
         pub si_code: ::c_int,
+        #[deprecated(
+            since="0.2.54",
+            note="Please leave a comment on \
+                https://github.com/rust-lang/libc/pull/1316 if you're using \
+                this field"
+        )]
         pub _pad: [::c_int; 29],
         #[cfg(target_arch = "x86_64")]
         _align: [u64; 0],
@@ -194,6 +200,19 @@ s! {
     }
 }
 
+impl siginfo_t {
+    pub unsafe fn si_addr(&self) -> *mut ::c_void {
+        #[repr(C)]
+        struct siginfo_sigfault {
+            _si_signo: ::c_int,
+            _si_errno: ::c_int,
+            _si_code: ::c_int,
+            si_addr: *mut ::c_void
+        }
+        (*(self as *const siginfo_t as *const siginfo_sigfault)).si_addr
+    }
+}
+
 s_no_extra_traits! {
     pub struct utmpx {
         pub ut_type: ::c_short,