logging: Extend log_target with call-back for un-formatted log line

Some targets might not want to receive only an opaque, pre-formatted
string, but rather the unformatted arguments with metadata like
sub-system/level/file/line.  We solve this by introducing a
log_target->output_raw() function pointer.  If a target specifies this
function, it takes precedence over the regular log_target->output()
function.

Change-Id: I9dc9205d70dce9581458e7e9dc2d8a92991897bd
2 files changed