#179433 and #178294. comments can get emailed even when unpublished and when belonging to an omitted node type.

rework og_mail query again so it is slightly less efficient but more accurate and compatible with postgres and any others.

eliminate duplicate email notfications by switching from DISTINCT() to GROUP BY. I need someone to check this query in Postgres and suggest a change as needed. I don't care which group is returned alon g with the subscriber's email address. I do care that the group info is consistent.

#175567 better fix for error in your SQL syntax in og_mail(). patch by grugnog2. modified by moshe weitzman.