auto merge of #4894 : nnethercote/servo/read-smaps, r=jdm

Here's example -m output after these changesets are applied:

```
_size (MiB)_: _category_
     2798.61: vsize
      136.80: resident
      142.89: resident-according-to-smaps
       97.84: - anonymous (rw-p)
       23.98: - /home/njn/moz/servo/components/servo/target/servo (r-xp)
        6.58: - [heap] (rw-p)
        5.36: - other
        3.51: - /usr/lib/x86_64-linux-gnu/dri/i965_dri.so (r-xp)
        1.33: - /lib/x86_64-linux-gnu/libc-2.19.so (r-xp)
        0.93: - /home/njn/moz/servo/components/servo/target/servo (r--p)
        0.76: - /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.20 (r-xp)
        0.74: - /usr/lib/x86_64-linux-gnu/libX11.so.6.3.0 (r-xp)
        0.50: - /lib/x86_64-linux-gnu/libcrypto.so.1.0.0 (r-xp)
        0.50: - /lib/x86_64-linux-gnu/libglib-2.0.so.0.4200.1 (r-xp)
        0.45: - /usr/lib/x86_64-linux-gnu/mesa/libGL.so.1.2.0 (r-xp)
        0.43: - /lib/x86_64-linux-gnu/libm-2.19.so (r-xp)
       30.85: system-heap-allocated
        4.91: jemalloc-heap-allocated
        6.11: jemalloc-heap-active
      120.00: jemalloc-heap-mapped
```
The `resident-according-to-smaps` line is new, as are all the indented lines beneath it. This is useful particularly because it shows how much memory is taken up by code, e.g. the line ending in `servo (r-xp)` shows that the `servo` executable's code alone takes up 24 MiB of physical memory.

0 files changed, 0 insertions, 0 deletions