use terminal title for status reports

[timo]

since the terminal output is oftentimes spammed with lots and lots of text, for example when building compilers from source, it'd be very helpful to have a quick way to figure out what perl6-bench is currently doing and how many other times it's going to do that same thing before doing another thing.

perl6-bench: building rakudo-jvm/2014.03 [3 of 10]
perl6-bench: timing rakudo-moar/2014.10 [10 of 10]
perl6-bench: stresstesting nqp-moar/2014.10 [1 of 1]

[timo]

actually, putting "perl6-bench" at the end rather than the front would make more sense, as well as putting the [n of m] in front, as terminal titles would usually be cut off after a few characters and that order would more accurately represent what's actually interesting