Fix incorrect stroke color bug in SynPDF

[iadcode]

This fix ensures that the stroke colour is reset when GRestore is called. The incorrect behaviour is triggered by the underline being rendered before the latter stroke. Before the change After the change

NB: The underline bug is being submitted as a separate PR (#422)

This behaviour can be tested with code such as

  procedure EmfToPdf(EmfFilename: String; PdfFilename: String);
  const
    C_PDFPPI = 72;
    C_MMperInch = 25.4;
  var
    PDFDocument: TPdfDocument;
    Metafile: TMetafile;
    Scale: Single;
  begin
    Metafile := TMetafile.Create;
    try
      Metafile.LoadFromFile(EmfFilename);
      PDFDocument := TPdfDocument.Create(False, 0, False);
      try
        PDFDocument.DefaultPaperSize := psA4;
        PDFDocument.ScreenLogPixels := C_PDFPPI;
        PDFDocument.AddPage;
        Scale := C_PDFPPI / Trunc((Metafile.Width * 100) / (Metafile.MMWidth / C_MMperInch));
        PDFDocument.Canvas.RenderMetaFile(Metafile, Scale, Scale, 0, 0, tpSetTextJustification, 99, 101, tcAlwaysClip);
        PDFDocument.SaveToFile(PdfFilename);
      finally
        FreeAndNil(PDFDocument);
      end;
    finally
      FreeAndNil(Metafile);
    end;
  end;

And using an EMF such as the one in this zip: BugsEMF.zip