Add a basic memory profiler, invoked with -m.

[nnethercote]

This adds a basic memory profiler. It's invoked with the -m option. Sample
output:

category : size (MiB)
vsize : 1355.47
resident : 50.85

It currently only works on Linux. On other platforms, "???" will be printed
instead.

I chose to make the memory profiler entirely separate from the existing
profiler, as opposed to augmenting it. They are/will be different enough beasts
that this seemed the right thing to do. But it did result in a bit of copy &
pasting. And if you run with both -p and -m, the output can be interleaved,
which isn't ideal.

Something I didn't do, which might make sense, is to rename Profiler (and all
related names) as TimeProfiler. That name would nicely match the |time| module
name.

The option_try! macro might be a useful thing to add to Rust's std::macros.

[hoppipolla-critic-bot]

Critic review: https://critic.hoppipolla.co.uk/r/1908

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[highfive]

Thanks for the pull request, and welcome! The Servo team is excited to review your changes, and you should hear from @jdm (or someone else) soon.

[pcwalton]

Sweet! r=me with nits addressed.

[nnethercote]

I addressed the minor nits except for the |Instrumentation| suggestion, because I couldn't work out how to create a new module, and it also felt like overkill. I also added a second patch that renames Profiler as TimeProfiler.

pcwalton, can you please re-review?

The Mac Travis CI run failed, but it looked like an infrastructure problem?

[larsbergstrom]

@nnethercote I'm looking into the travisci failure - it appears to be a network timeout installing autoconf213, which is required by our ancient version of SpiderMonkey.

[larsbergstrom]

On TravisCI, I get:

/libmacros.dummy

/Users/travis/build/mozilla/servo/src/components/util/memory.rs:8:5: 8:18 error: unused import [-D unused-imports]

/Users/travis/build/mozilla/servo/src/components/util/memory.rs:8 use std::io::File;

^~~~~~~~~~~~~

/Users/travis/build/mozilla/servo/src/components/util/memory.rs:9:5: 9:23 error: unused import [-D unused-imports]

/Users/travis/build/mozilla/servo/src/components/util/memory.rs:9 use std::os::page_size;

[nnethercote]

I fixed the Mac-only travis errors and rebased. Should be good for re-review now.