liblog: logprint, error return and truncated data

android_log_processBinaryLogBuffer and android_log_processLogBuffer
error return should have message and messageLen fields set to zero,
or to a valid-but-truncated buffer so that we can discern the
difference.  This will resolve an issue with reporting content from
an uninitialized field in liblogcat should caller add --debug flag.

To enhance the debugging capability, truncated string events because
of the logger limits are provided rather than dropping the field, but
still with an error return.

Some minor coding style issues resolved. Add required, or remove
extraneous spaces.  Use C-style comments only.

Test: gtest liblog-unit-tests
Bug: 27405083
Bug: 35326290
Change-Id: I4a7ddd7278fb1c582f921e1ba10e0765fadb791b