add a trait for mutable iterators
hide the linkhack module in the docs
rm FIXME from use of #[doc(hidden)] on pub mod
rustdoc: Filter out private definitions. Closes #3538
auto merge of #5367 : brson/rust/5299, r=thestinger

r?
auto merge of #5369 : thestinger/rust/iter, r=z0w0

This can eventually be implemented on other sequence containers like `deque` (it's missing `each` too at the moment).
auto merge of #5371 : thestinger/rust/hidden, r=pcwalton
MutableIter impl for Option + use it in treemap
auto merge of #5375 : z0w0/rust/rustdoc-private-hide, r=thestinger
auto merge of #5395 : thestinger/rust/iter, r=pcwalton
Add a way to run the test suite with the new scheduler

TESTARGS=--newrt make check-stage1-rpass