Mark public non-member non-static variables as Q_DECL_UNUSED

This avoids warnings in compilers that check for unused variables. They
can't tell that the the variable came from a header.

Change-Id: I1ea5e5bbc76d676fbb561bdc8ae6543e758de90e
Reviewed-by: Andreas Aardal Hanssen <andreas@hanssen.name>
Reviewed-by: Gunnar Sletta <gunnar.sletta@digia.com>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

src/gui/painting/qrgb.h

@@ -49,7 +49,8 @@ QT_BEGIN_NAMESPACE
 
 typedef unsigned int QRgb;                        // RGB triplet
 
-const QRgb  RGB_MASK    = 0x00ffffff;                // masks RGB values
+// non-namespaced Qt global variable
+const Q_DECL_UNUSED QRgb  RGB_MASK    = 0x00ffffff;     // masks RGB values
 
 inline int qRed(QRgb rgb)                // get red part of RGB
 { return ((rgb >> 16) & 0xff); }

src/widgets/kernel/qlayoutitem.h

@@ -50,7 +50,7 @@
 QT_BEGIN_NAMESPACE
 
 
-static const int QLAYOUTSIZE_MAX = INT_MAX/256/16;
+static const Q_DECL_UNUSED int QLAYOUTSIZE_MAX = INT_MAX/256/16;
 
 class QLayout;
 class QLayoutItem;