replaced "foldl merge_theories" by "merge_thy_list" in base_on
replaced "foldl merge_theories" by "merge_thy_list" in base_on

MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle