Replace all uses of the heapsize crate with malloc_size_of.

Servo currently uses `heapsize`, but Stylo/Gecko use `malloc_size_of`.
`malloc_size_of` is better -- it handles various cases that `heapsize` does not
-- so this patch changes Servo to use `malloc_size_of`.

This patch makes the following changes to the `malloc_size_of` crate.

- Adds `MallocSizeOf` trait implementations for numerous types, some built-in
  (e.g. `VecDeque`), some external and Servo-only (e.g. `string_cache`).

- Makes `enclosing_size_of_op` optional, because vanilla jemalloc doesn't
  support that operation.

- For `HashSet`/`HashMap`, falls back to a computed estimate when
  `enclosing_size_of_op` isn't available.

- Adds an extern "C" `malloc_size_of` function that does the actual heap
  measurement; this is based on the same functions from the `heapsize` crate.

This patch makes the following changes elsewhere.

- Converts all the uses of `heapsize` to instead use `malloc_size_of`.

- Disables the "heapsize"/"heap_size" feature for the external crates that
  provide it.

- Removes the `HeapSizeOf` implementation from `hashglobe`.

- Adds `ignore` annotations to a few `Rc`/`Arc`, because `malloc_size_of`
  doesn't derive those types, unlike `heapsize`.

components/script_traits/Cargo.toml

@@ -16,12 +16,12 @@ cookie = "0.6"
 devtools_traits = {path = "../devtools_traits"}
 euclid = "0.15"
 gfx_traits = {path = "../gfx_traits"}
-heapsize = "0.4"
-heapsize_derive = "0.1"
 hyper = "0.10"
 hyper_serde = "0.7"
 ipc-channel = "0.9"
 libc = "0.2"
+malloc_size_of = { path = "../malloc_size_of" }
+malloc_size_of_derive = { path = "../malloc_size_of_derive" }
 msg = {path = "../msg"}
 net_traits = {path = "../net_traits"}
 profile_traits = {path = "../profile_traits"}
@@ -31,6 +31,6 @@ servo_atoms = {path = "../atoms"}
 servo_url = {path = "../url"}
 style_traits = {path = "../style_traits", features = ["servo"]}
 time = "0.1.12"
-url = {version = "1.2", features = ["heap_size"]}
+url = "1.2"
 webrender_api = {git = "https://github.com/servo/webrender", features = ["ipc"]}
 webvr_traits = {path = "../webvr_traits"}