Remove handle duplication code from QWindowsPipeWriter

There is no apparent reason why the handle should be duplicated.

Change-Id: I8ff2cde2f050934ed0dd9ab2d39a1b1efa327a17
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>

src/corelib/io/qwindowspipewriter.cpp

@@ -39,12 +39,10 @@ QT_BEGIN_NAMESPACE
 
 QWindowsPipeWriter::QWindowsPipeWriter(HANDLE pipe, QObject * parent)
     : QThread(parent),
-      writePipe(INVALID_HANDLE_VALUE),
+      writePipe(pipe),
       quitNow(false),
       hasWritten(false)
 {
-    DuplicateHandle(GetCurrentProcess(), pipe, GetCurrentProcess(),
-                         &writePipe, 0, FALSE, DUPLICATE_SAME_ACCESS);
 }
 
 QWindowsPipeWriter::~QWindowsPipeWriter()
@@ -55,7 +53,6 @@ QWindowsPipeWriter::~QWindowsPipeWriter()
     lock.unlock();
     if (!wait(30000))
         terminate();
-    CloseHandle(writePipe);
 }
 
 bool QWindowsPipeWriter::waitForWrite(int msecs)