CONTRIB: debug: add the possibility to decode the value as certain types only

CONTRIB: debug: add the possibility to decode the value as certain types only

It's often confusing to have a whole dump on the screen while only
checking for a set of task or stream flags, and appending "|grep ^chn"
isn't very convenient to repeat the opeation. Instead let's add the
ability to filter the output as certain types only by prepending their
name(s) before the value.