Fix wrong use of Q_UNUSED

So my previous build test might failed.
I will keep this change history as a part of working process.

This will not be stay in clean branch for pull request.
Port to Qt5 Fix all Q_OS_*/Q_WS_* globals.

This commit has untested changes,
because of the change effects to various platform.

Now I follow qt5 porting guide document.

  Platform defines - All platform-specific code must be wrapped
  using the preprocessor macro, Q_OS* instead of Q_WS*.

Qt-5.x does not have Q_WS_* anymore,
Qt-5.x and Qt-4.x both has Q_OS_* in QtGlobal header.

The implementation is QtCore/qsystemdetection.h
The header file has more defined macro information than document.

Qt-5.x, those Q_WS_* macro were not defined,
Thise codes are not right anymore, but still can pass build

  #ifdef Q_WS_WIN
    // ...
  #else
    // compile code here in Windows/Qt-5.x
  #endif

To be fail safe, enum all available support platform macro.
and #else case always raise error for unsupport platform.
But Q_WS_* had only 5, Q_OS_* has many. this may cost to
write all available platforms. and that rule may be too strict
for another unix-like platform which may success build with
same code. Q_OS_UNIX is for the !defined(Q_OS_WIN) case.

This is up to policy inclusive-explicitly or exclusive-implicitly
The second case has problem unexpected code in unsupported platform.

The first case, to support widely similar posix compatible platform,
There is traditional way, checking the function is aveirable
on the configure time (autoconf)

But as an application code,
For now, support Q_OS_LINX, Q_OS_MAC, Q_OS_WIN are enough
as well as support main target platform distribute binaries.

I will just leave this as note.
This commit just rename macro as following porting guide.

Signed-off-by: Ikkei Shimomura (tea) <Ikkei.Shimomura@gmail.com>