Extract ioctl to <bits/ioctl.h>.

Bug: http://b/28067717
Change-Id: I93625d19fa5a033ab22c650d536e98674f0a8d9d
diff --git a/libc/include/unistd.h b/libc/include/unistd.h
index 0e5fcb0..b6046be 100644
--- a/libc/include/unistd.h
+++ b/libc/include/unistd.h
@@ -36,6 +36,7 @@
 #include <sys/sysconf.h>
 
 #include <bits/fcntl.h>
+#include <bits/ioctl.h>
 #include <bits/lockf.h>
 #include <bits/posix_limits.h>
 
@@ -162,7 +163,6 @@
 extern int dup(int __oldfd);
 extern int dup2(int __oldfd, int __newfd);
 extern int dup3(int __oldfd, int __newfd, int __flags) __INTRODUCED_IN(21);
-extern int ioctl(int __fd, int __request, ...);
 extern int fsync(int __fd);
 extern int fdatasync(int __fd) __INTRODUCED_IN(9);