Handle new current.txt format.

We're starting to see "@interface" show up, so handle them like any
other interface.  We're also seeing more details argument lists
with names and annotations; ignore them for now, since all our
existing lint checks work on the "real" data type.

Verified that it handles new support library current.txt files
without causing any regressions against existing framework
current.txt files.

Test: manual inspection
Bug: 111555356
Change-Id: Id11c3561edd317e4ba1a9b43993fd96d8243e00d
(cherry picked from commit bd261191)