Add htonl, htons, ntohl, ntohs

(backport <#3669>)
(cherry picked from commit 1feb354)

Author: Askar Safin

libc-test/semver/unix.txt

@@ -588,6 +588,8 @@ grantpt
 group
 hostent
 hstrerror
+htonl
+htons
 if_indextoname
 if_nametoindex
 in6_addr
@@ -658,6 +660,8 @@ munmap
 nanosleep
 nfds_t
 nlink_t
+ntohl
+ntohs
 off_t
 open
 opendir

src/unix/mod.rs

@@ -1446,6 +1446,23 @@ extern "C" {
 
 }
 
+safe_f! {
+    // It seems htonl, etc are macros on macOS. So we have to reimplement them. So let's
+    // reimplement them for all UNIX platforms
+    pub {const} fn htonl(hostlong: u32) -> u32 {
+        u32::to_be(hostlong)
+    }
+    pub {const} fn htons(hostshort: u16) -> u16 {
+        u16::to_be(hostshort)
+    }
+    pub {const} fn ntohl(netlong: u32) -> u32 {
+        u32::from_be(netlong)
+    }
+    pub {const} fn ntohs(netshort: u16) -> u16 {
+        u16::from_be(netshort)
+    }
+}
+
 cfg_if! {
     if #[cfg(not(any(target_os = "emscripten",
                      target_os = "android",