option to toggle flamegraph to threaded view

[ceeaspb]

We often need to review individual threads for load balancing, utilisation, etc.
Being able to toggle between the 2 views would be very useful.
It would need source data in the perf script output according to stackcollapse-perf.pl.

USAGE: ./stackcollapse-perf.pl [options] infile > outfile

	--tid		# include TID and PID with process names [1]
...

[1] perf script must emit both PID and TIDs for these to work; eg, Linux < 4.1:
	perf script -f comm,pid,tid,cpu,time,event,ip,sym,dso,trace
    for Linux >= 4.1:
	perf script -F comm,pid,tid,cpu,time,event,ip,sym,dso,trace