Fix the definition differences issue of termios.h in different version of kernel header and cygwin's include files.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@2622 6f19259b-4bc3-4df7-8a09-765794883524

EdkUnixPkg/Sec/UnixThunk.c

@@ -40,6 +40,8 @@ Abstract:
 #include <stdlib.h>
 #include <termio.h>
 
+extern ioctl (int fd, unsigned long int __request, ...);
+
 static int settimer_initialized;
 static struct timeval settimer_timeval;
 static void (*settimer_callback)(UINT64 delta);