WIP: don't report subprocess names in SVG output

[smason]

I'd like some way of suppressing subprocess info in the flamegraph/SVG output. This pull-request doesn't expose this option to the user, but seems to do the right thing when I run it.

The motivation is when using the multiprocessing module (e.g. the code below) and hence I don't really care which process the code is running inside, just that it's not in the main one probably. I.e. when running the official version I get n processes that contain basically the same information and hence it seems to make sense to combine them into a single stack. This transformation obviously doesn't make sense if the user is doing different things in each process, but for multiprocessing workloads this cleans up the output a lot.

I think this functionality should be exposed on the command-line somewhere, but wasn't sure how to do that nicely so left that out for the time being.

from multiprocessing import Pool
from time import monotonic

def foo(x):
    t1 = monotonic() + 0.1
    while monotonic() < t1:
        x += sum(range(1024 * 1024))
    return x

def main():
    with Pool() as pool:
        print(pool.map(foo, range(100)))

if __name__ == "__main__":
    main()