libbinder: Status s/stringstream/ostream/

stringstream extends ostream, so this is just generally more useful.
I'm tired of having to lookup that I need to use 'Status::toString8' in
order to print it out.

Test: m camera_client_test (uses API, motived last change here)
Test: grep most internal prebuilts for
_ZN7android6binderlsERNSt3__118basic_stringstreamIcNS1_11char_traitsIcEENS1_9allocatorIcEEEERKNS0_6StatusE

Change-Id: I7ed88a3ecf8b560302697e4c5c2357acc05c20fa