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/Cargo.toml

@@ -44,9 +44,7 @@ euclid = "0.15"
 fnv = "1.0"
 gleam = "0.4"
 half = "1.0"
-heapsize = "0.4"
-heapsize_derive = "0.1"
-html5ever = {version = "0.20", features = ["heap_size"]}
+html5ever = "0.20"
 hyper = "0.10"
 hyper_serde = "0.7"
 image = "0.16"
@@ -56,6 +54,8 @@ jstraceable_derive = {path = "../jstraceable_derive"}
 lazy_static = "0.2"
 libc = "0.2"
 log = "0.3.5"
+malloc_size_of = { path = "../malloc_size_of" }
+malloc_size_of_derive = { path = "../malloc_size_of_derive" }
 metrics = {path = "../metrics"}
 mitochondria = "1.1.2"
 mime = "0.2.1"
@@ -89,7 +89,7 @@ style_traits = {path = "../style_traits"}
 swapper = "0.1"
 time = "0.1.12"
 unicode-segmentation = "1.1.0"
-url = {version = "1.2", features = ["heap_size", "query_encoding"]}
+url = {version = "1.2", features = ["query_encoding"]}
 utf-8 = "0.7"
 uuid = {version = "0.5", features = ["v4"]}
 xml5ever = {version = "0.10"}