Auto merge of #1101 - koutheir:master, r=alexcrichton

Added dup3() support on FreeBSD, NetBSD, OpenBSD and Solaris

Added `dup3()` support on FreeBSD, NetBSD, OpenBSD and Solaris.

The `dup3()` API is present in:
- FreeBSD 10.0 an later.
- NetBSD 6.0 and later.
- OpenBSD 5.7 and later.
- Solaris 11.4 and later.

Author: bors

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

@@ -1056,6 +1056,8 @@ extern {
 
     pub fn statfs(path: *const ::c_char, buf: *mut statfs) -> ::c_int;
     pub fn fstatfs(fd: ::c_int, buf: *mut statfs) -> ::c_int;
+
+    pub fn dup3(src: ::c_int, dst: ::c_int, flags: ::c_int) -> ::c_int;
 }
 
 cfg_if! {

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

@@ -1106,6 +1106,8 @@ extern {
                      base: ::locale_t) -> ::locale_t;
     #[link_name = "__settimeofday50"]
     pub fn settimeofday(tv: *const ::timeval, tz: *const ::c_void) -> ::c_int;
+
+    pub fn dup3(src: ::c_int, dst: ::c_int, flags: ::c_int) -> ::c_int;
 }
 
 #[link(name = "util")]

src/unix/bsd/netbsdlike/openbsdlike/openbsd/mod.rs

@@ -263,6 +263,8 @@ extern {
 
     pub fn statfs(path: *const ::c_char, buf: *mut statfs) -> ::c_int;
     pub fn fstatfs(fd: ::c_int, buf: *mut statfs) -> ::c_int;
+
+    pub fn dup3(src: ::c_int, dst: ::c_int, flags: ::c_int) -> ::c_int;
 }
 
 cfg_if! {

src/unix/solaris/mod.rs

@@ -1458,4 +1458,6 @@ extern {
     pub fn getgrgid(gid: ::gid_t) -> *mut ::group;
     pub fn popen(command: *const c_char,
                  mode: *const c_char) -> *mut ::FILE;
+
+    pub fn dup3(src: ::c_int, dst: ::c_int, flags: ::c_int) -> ::c_int;
 }