Auto merge of #2097 - cmusser:topic/dfly-waitid, r=JohnTitor

dragonflybsd: expose waitid() prototype + related constants

This exposes the POSIX waitid() process management function and some related defined constants for dragonflybsd. It includes one correction: WSTOPPED which previously had the wrong value. Noticed this when a crate that depended on it, process_control, wouldn't compile on this platform.

src/unix/bsd/freebsdlike/dragonfly/mod.rs

@@ -17,6 +17,7 @@ pub type uuid_t = ::uuid;
 
 pub type fsblkcnt_t = u64;
 pub type fsfilcnt_t = u64;
+pub type idtype_t = ::c_uint;
 
 pub type mqd_t = ::c_int;
 pub type sem_t = *mut sem;
@@ -982,8 +983,17 @@ pub const _SC_V7_LPBIG_OFFBIG: ::c_int = 125;
 pub const _SC_THREAD_ROBUST_PRIO_INHERIT: ::c_int = 126;
 pub const _SC_THREAD_ROBUST_PRIO_PROTECT: ::c_int = 127;
 
-pub const WCONTINUED: ::c_int = 4;
-pub const WSTOPPED: ::c_int = 0o177;
+pub const WCONTINUED: ::c_int = 0x4;
+pub const WSTOPPED: ::c_int = 0x2;
+pub const WNOWAIT: ::c_int = 0x8;
+pub const WEXITED: ::c_int = 0x10;
+pub const WTRAPPED: ::c_int = 0x20;
+
+// Similar to FreeBSD, only the standardized ones are exposed.
+// There are more.
+pub const P_PID: idtype_t = 0;
+pub const P_PGID: idtype_t = 2;
+pub const P_ALL: idtype_t = 7;
 
 // Values for struct rtprio (type_ field)
 pub const RTP_PRIO_REALTIME: ::c_ushort = 0;
@@ -1061,6 +1071,13 @@ extern "C" {
         timeout: *mut ::timespec,
     ) -> ::c_int;
 
+    pub fn waitid(
+        idtype: idtype_t,
+        id: ::id_t,
+        infop: *mut ::siginfo_t,
+        options: ::c_int,
+    ) -> ::c_int;
+
     pub fn freelocale(loc: ::locale_t);
 
     pub fn lwp_rtprio(