'hydroPSO': immproved checking of some arguments; 'random.update' only used when 'best.update'=async, and more and better examples. 'text\_functions': corrected name of the 'rastringin' function, and corrected definition of the 'shafferF6' function

Fixed error that appeared when the 'plot_out' function was called from an R script running directly on the OS console (not within the R editor), with the following error message: 'Error in plot2(x = sim, y = obs, plot.type = single, main = paste('Daily',  : could not find function 'hasArg'