Async-profiler: Add munmap and free to known functions

[oehme]

To my delight, I noticed that -e mmap --total and -e malloc --total work and show how much was allocated instead of how often :tada:. I think this deserves to be documented btw.

It would be cool if munmap and free would be treated the same. That way I could trace those pairs of events and see if they have the same width on the flame graph. Not every call to mmap is a leak, there are libraries that call mmap and munmap directly, e.g. some encryption libraries. It's only a problem if they mmap more than they munmap.

[apangin]

My plan is to generalize counting total of an arbitrary function that takes an integer argument. It will be possible to specify which argument to track: e.g. the first argument of malloc, or the second argument of mmap or munmap.

Unfortunately, free accepts only an address - it's hard to determine how much memory is freed. In theory, it's possible to sample malloc'ed addresses and match them with corresponding free calls - but I'm afraid it falls out of the scope of async-profiler. After all, some native allocators (like jemalloc) already have this feature.

[oehme]

I guess free isn't as important anyway, as mmap is how you see the live set increase.

[apangin]

Added munmap to the known list.

Also, it's now possible to specify which argument to use for total,
e.g. -e sendfile{4} means profile the fourth argument of sendfile().