ChangeLog with .0 for 3.6 release.
Note 3.6 leak fixes in bug section.

(cherry picked from commit 7d3b47c3ed54f821cea47f4c8c8c90333d46fa47)
Spaces not tabs in 3.6 change list.

(cherry picked from commit e32566e4e261e501f12b0695c33d7f50864823de)