3.5.17 TextMark sample

Function textmark like Mark but draw text instead of markers. The sample code is:

int sample(mglGraph *gr)
{
  mglData y,y1; mgls_prepare1d(&y,&y1);
  gr->SubPlot(1,1,0,"");  gr->Title("TextMark plot (default)");
  gr->Box();  gr->TextMark(y,y1,"\\gamma","r");
  return 0;
}