logcat: support --regex on binary buffers as-is

(cherry pick from commit aa730c11)

- Do not restrict regex on LOG_ID_EVENTS or LOG_ID_SECURITY.
- some logcat_panic messages need to incorporate a newline.
- deal with some coding standards issues.

Bug: 27706081
Change-Id: Ie647fd62d027b01004177559d68b8e5a346705e6