Unify the ioctl declarations on linux

This uses the existing Ioctl type to reduce the duplication.

(backport <rust-lang#3722>)
(cherry picked from commit 01a3617)

src/unix/linux_like/linux/gnu/mod.rs

@@ -1405,7 +1405,6 @@ extern "C" {
     pub fn reallocarray(ptr: *mut ::c_void, nmemb: ::size_t, size: ::size_t) -> *mut ::c_void;
 
     pub fn ctermid(s: *mut ::c_char) -> *mut ::c_char;
-    pub fn ioctl(fd: ::c_int, request: ::c_ulong, ...) -> ::c_int;
     pub fn backtrace(buf: *mut *mut ::c_void, sz: ::c_int) -> ::c_int;
     pub fn glob64(
         pattern: *const ::c_char,

src/unix/linux_like/linux/mod.rs

@@ -5635,6 +5635,8 @@ extern "C" {
     ) -> ::ssize_t;
 
     pub fn klogctl(syslog_type: ::c_int, bufp: *mut ::c_char, len: ::c_int) -> ::c_int;
+
+    pub fn ioctl(fd: ::c_int, request: ::Ioctl, ...) -> ::c_int;
 }
 
 // LFS64 extensions

src/unix/linux_like/linux/musl/mod.rs

@@ -853,7 +853,6 @@ extern "C" {
         new_limit: *const ::rlimit,
         old_limit: *mut ::rlimit,
     ) -> ::c_int;
-    pub fn ioctl(fd: ::c_int, request: ::c_int, ...) -> ::c_int;
     pub fn gettimeofday(tp: *mut ::timeval, tz: *mut ::c_void) -> ::c_int;
     pub fn ptrace(request: ::c_int, ...) -> ::c_long;
     pub fn getpriority(which: ::c_int, who: ::id_t) -> ::c_int;

src/unix/linux_like/linux/uclibc/mod.rs

@@ -353,7 +353,6 @@ pub const UDP_SEGMENT: ::c_int = 103;
 pub const YESEXPR: ::c_int = ((5) << 8) | (0);
 
 extern "C" {
-    pub fn ioctl(fd: ::c_int, request: ::c_ulong, ...) -> ::c_int;
     pub fn gettimeofday(tp: *mut ::timeval, tz: *mut ::timezone) -> ::c_int;
 
     pub fn pthread_rwlockattr_getkind_np(