2009-07-31 Andreas J. Guelzow <aguelzow@pyrshep.ca>

	* dialog-analysis-tools.c (dialog_*_tool): check for
	  required plugins
	* dialog-analysis-tool-chi-squared.c (dialog_chi_square_tool):
	  ditto
	* dialog-analysis-tool-frequency.c (dialog_frequency_tool):
	  ditto
	* dialog-analysis-tool-kaplan-meier.c (dialog_kaplan_meier_tool):
	  ditto