The pains_pre_aminal1 rule has been removed from the PAINS filter. The
SMARTS for the rule was incorrectly defined and was overly general. The
rules pains_basic_amine1, pains_basic_amine2, and
pains_basic_amine3 cover the same general structural classes in a more
precise manner. A SMARTS issue with the pains_basic_amine3, uncovered
after removing the pains_pre_aminal1 rule, has also been corrected.