Optimize PostScript code generated by wxPostScriptDC

PostScript code to register (and re-encode) given font should be emitted only once. Once registered, the font is available in the entire document and there is no need to register it again.

include/wx/generic/dcpsg.h

@@ -150,6 +150,7 @@ protected:
     double            m_underlineThickness;
     wxPrintData       m_printData;
     double            m_pageHeight;
+    wxArrayString     m_definedPSFonts;
 
 private:
     wxDECLARE_DYNAMIC_CLASS(wxPostScriptDCImpl);