Add ENOTSUP to Linux and Android

While ENOTSUP is defined as equal to EOPNOTSUPP on these platforms,
exposing the ENOTSUP symbol (as libc does) allows for writing portable
code that may want to reference this error code.

Author: jmmv

CHANGELOG.md

@@ -7,9 +7,10 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 ### Added
 - Add IP_RECVIF & IP_RECVDSTADDR. Enable IP_PKTINFO and IP6_PKTINFO on netbsd/openbsd.
   ([#1002](https://github.com/nix-rust/nix/pull/1002))
-
 - Added `inotify_init1`, `inotify_add_watch` and `inotify_rm_watch` wrappers for
   Android and Linux. ([#1016](https://github.com/nix-rust/nix/pull/1016))
+- Added ENOTSUP errno support for Linux and Android.
+  ([#969](https://github.com/nix-rust/nix/pull/969))
 
 ### Changed
 - `PollFd` event flags renamed to `PollFlags` ([#1024](https://github.com/nix-rust/nix/pull/1024/))

src/errno.rs

@@ -675,6 +675,7 @@ mod consts {
 
     pub const EWOULDBLOCK: Errno = Errno::EAGAIN;
     pub const EDEADLOCK:   Errno = Errno::EDEADLK;
+    pub const ENOTSUP:     Errno = Errno::ENOTSUP;
 
     pub fn from_i32(e: i32) -> Errno {
         use self::Errno::*;