(Bug 5026) Add yyyy/mm/dd format
(Bug 5026) Limit how many lines back we look

To reduce the chance that we accidentally snip mid-message.
(Bug 5026) Another date format

On Apr xx, xxxx...
(Bug 5026) Recognize ---Original Message--- separator
Merge pull request #358 from afuna/general-on-wrote-bug5026

(Bug 5026) Recognize more formats of separators before the quoted message