Stop using wxColourDisplay() inside wxWidgets code

This function always returns true in practice and it's completely
useless to call it during each wxDC object construction, especially
because wxDC::m_colour itself is not used anywhere.

src/common/dcsvg.cpp

@@ -402,7 +402,6 @@ void wxSVGFileDCImpl::Init(const wxString &filename, int Width, int Height,
     m_backgroundBrush = *wxTRANSPARENT_BRUSH;
     m_textForegroundColour = *wxBLACK;
     m_textBackgroundColour = *wxWHITE;
-    m_colour = wxColourDisplay();
 
     m_pen   = *wxBLACK_PEN;
     m_font  = *wxNORMAL_FONT;