Round physical bitmap size in wxGTK wxBitmap::CreateScaled()

Round the result of the multiplication by possibly non-integer scaling
factor rather than truncating it. This is more consistent with wxMSW and
other ports not using DIPs (wxOSX doesn't matter, as the scale factor
can only be an integer there anyhow) and seems to be more useful.

E.g. previously creating a bitmap of logical size 5 at 150% DPI scaling
would create a 7px bitmap, for which GetLogicalWidth() would return 4.66
that would be truncated to 4, and not 5, when assigning it to an int,
while now a 8px bitmap will be created and both rounding or truncating
its GetLogicalWidth() value of 5.33 results in the more expected 5.

src/gtk/bitmap.cpp

@@ -18,6 +18,7 @@
     #include "wx/cursor.h"
 #endif
 
+#include "wx/math.h"
 #include "wx/rawbmp.h"
 
 #include "wx/gtk/private/object.h"
@@ -991,7 +992,7 @@ void wxBitmap::SetMask( wxMask *mask )
 #ifdef __WXGTK3__
 bool wxBitmap::CreateScaled(int w, int h, int depth, double scale)
 {
-    Create(int(w * scale), int(h * scale), depth);
+    Create(wxRound(w * scale), wxRound(h * scale), depth);
     M_BMPDATA->m_scaleFactor = scale;
     return true;
 }