Revises comments to make it clear that the timer structure and
its fields are not part of the public API. Also eliminates an
unnecessary forward reference issue by defining the linked list
fields of the timer structure using the structure name itself.
Change-Id: Ic6489c38ab4e3a6408a0b9475bdd2956ae51c4a4
Signed-off-by: Allan Stephens <allan.stephens@windriver.com>