Merge branch 'la/hide-trailer-info'

The trailer API has been reshuffled a bit. * la/hide-trailer-info: trailer unit tests: inspect iterator contents trailer: document parse_trailers() usage trailer: retire trailer_info_get() from API trailer: make trailer_info struct private trailer: make parse_trailers() return trailer_info pointer interpret-trailers: access trailer_info with new helpers sequencer: use the trailer iterator trailer: teach iterator about non-trailer lines trailer: add unit tests for trailer iterator Makefile: sort UNIT_TEST_PROGRAMS