android: logger: Allow a UID to read it's own log entries

Modify the kernel logger to record the UID associated with
the log entries. Always allow the same UID which generated a
log message to read the log message.

Allow anyone in the logs group, or anyone with CAP_SYSLOG, to
read all log entries.

In addition, allow the client to upgrade log formats, so they
can get additional information from the kernel.

Change-Id: Ie48fb614b43c9302a07ad2673b78dd8749b492b6
Signed-off-by: Nick Kralevich <nnk@google.com>