option.get -> option.unwrap
std: add result.map_move, result.map_err_move
core: option.map_consume -> option.map_move
std: removed option.take_map{,_default}
Add frequency count to extra::stat. #8281
auto merge of #8294 : erickt/rust/map-move, r=bblum

According to #7887, we've decided to use the syntax of `fn map<U>(f: &fn(&T) -> U) -> U`, which passes a reference to the closure, and to `fn map_move<U>(f: &fn(T) -> U) -> U` which moves the value into the closure. This PR adds these `.map_move()` functions to `Option` and `Result`.

In addition, it has these other minor features:
 
* Replaces a couple uses of `option.get()`, `result.get()`, and `result.get_err()` with `option.unwrap()`, `result.unwrap()`, and `result.unwrap_err()`. (See #8268 and #8288 for a more thorough adaptation of this functionality.
* Removes `option.take_map()` and `option.take_map_default()`. These two functions can be easily written as `.take().map_move(...)`.
* Adds a better error message to `result.unwrap()` and `result.unwrap_err()`.
auto merge of #8320 : mihneadb/rust/freq_count, r=cmr
std::rt: 2MB stacks again
std::rt: Pull RUST_MIN_STACK from the environment
std: Allow spawners to specify stack size
rustc: Use 4MB stacks. Needed for unoptimized builds apparently.
rustpkg: Disable test_uninstall

Seems to not work
test: xfail a bunch of tests that are incorrectly reading os::args()[1]
test: Fix deadlock in task-perf-linked-failure
xfail debug-info/option-like-enum

Don't understand why this broke.
doc: Fix deadlocks in tutorial due to yield bustage
Disable linked failure tests

The implementation currently contains a race that leads to segfaults.
rusti: Disable tests

Segfaulted on one of the bots. Maybe out of stack?
Turn on the new runtime
auto merge of #8358 : brson/rust/newrt, r=brson