OpenBSD: add sendmmsg and recvmmsg support.

close #3696

Author: devnexen

libc-test/semver/openbsd.txt

@@ -1210,6 +1210,7 @@ readlinkat
 reallocarray
 reboot
 recvmsg
+recvmmsg
 regcomp
 regerror
 regex_t

src/unix/bsd/netbsdlike/mod.rs

@@ -858,6 +858,20 @@ extern "C" {
     pub fn dirname(path: *mut ::c_char) -> *mut ::c_char;
     pub fn basename(path: *mut ::c_char) -> *mut ::c_char;
     pub fn getentropy(buf: *mut ::c_void, buflen: ::size_t) -> ::c_int;
+
+    pub fn sendmmsg(
+        sockfd: ::c_int,
+        mmsg: *mut ::mmsghdr,
+        vlen: ::c_uint,
+        flags: ::c_int,
+    ) -> ::c_int;
+    pub fn recvmmsg(
+        sockfd: ::c_int,
+        mmsg: *mut ::mmsghdr,
+        vlen: ::c_uint,
+        flags: ::c_int,
+        timeout: *mut ::timespec,
+    ) -> ::c_int;
 }
 
 cfg_if! {

src/unix/bsd/netbsdlike/netbsd/mod.rs

@@ -2750,20 +2750,6 @@ extern "C" {
 
     pub fn kqueue1(flags: ::c_int) -> ::c_int;
 
-    pub fn sendmmsg(
-        sockfd: ::c_int,
-        msgvec: *mut ::mmsghdr,
-        vlen: ::c_uint,
-        flags: ::c_int,
-    ) -> ::c_int;
-    pub fn recvmmsg(
-        sockfd: ::c_int,
-        msgvec: *mut ::mmsghdr,
-        vlen: ::c_uint,
-        flags: ::c_int,
-        timeout: *mut ::timespec,
-    ) -> ::c_int;
-
     pub fn _lwp_self() -> lwpid_t;
     pub fn memmem(
         haystack: *const ::c_void,