tools lib traceevent: Introduce new libtracevent API: tep_override_comm()

This patch adds a new API of tracevent library: tep_override_comm() It
registers a pid / command mapping. If a mapping with the same pid
already exists, the entry is updated with the new command.

Signed-off-by: Tzvetomir Stoyanov <tstoyanov@vmware.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/20181130154648.038915912@goodmis.org


Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>