hwpmc: log name->pid, name->tid mappings

By logging all threads and processes 'pmc filter'
can now filter on process or thread name, relieving
the user of the burden of determining which tid or
pid was which when the sample was taken.

% pmc filter -T if_io_tqg -P nginx pmc.log pmc-iflib.log

% pmc filter -x -T idle pmc.log pmc-noidle.log