Move duplicated code to the shared function

Code to emit PostScript commands to set the current colour is duplicated in several places (in SetBrush, SetPen, DrawAnyText functions) and therefore should be moved to a dedicated function.

include/wx/generic/dcpsg.h

@@ -141,6 +141,8 @@ protected:
     void DrawAnyText(const wxWX2MBbuf& textbuf, wxCoord testDescent, double lineHeight);
     // Actually set PostScript font
     void SetPSFont();
+    // Set PostScript color
+    void SetPSColour(const wxColour& col);
 
     FILE*             m_pstream;    // PostScript output stream
     unsigned char     m_currentRed;