Clean up DrawText() and DrawRotatedText() (wxPostScriptDC)

Move shared code to the separate method DrawAnyText() instead of duplicating it.

include/wx/generic/dcpsg.h

@@ -137,6 +137,9 @@ protected:
     void DoGetSize(int* width, int* height) const wxOVERRIDE;
     void DoGetSizeMM(int *width, int *height) const wxOVERRIDE;
 
+    // Common part of DoDrawText() and DoDrawRotatedText()
+    void DrawAnyText(const wxWX2MBbuf& textbuf, wxCoord testDescent);
+
     FILE*             m_pstream;    // PostScript output stream
     unsigned char     m_currentRed;
     unsigned char     m_currentGreen;