Implement highlight specific for Fortran77.

def highlight_block(self, text):
        """Implement highlight specific for Fortran77."""
        text = to_text_string(text)
        if text.startswith(("c", "C")):
            self.setFormat(0, len(text), self.formats["comment"])
            self.highlight_spaces(text)
        else:
            FortranSH.highlight_block(self, text)
            self.setFormat(0, 5, self.formats["comment"])
            self.setFormat(73, max([73, len(text)]),
                           self.formats["comment"])