Renamed Option::map_default and mutate_default to map_or and mutate_or_set
libextra: Introduce typed arenas.

A typed arena is a type of arena that can only allocate objects of one
type. It is 3x faster than the existing arena and 13x faster than malloc
on Mac.
auto merge of #10854 : Kimundi/rust/result_compose_map_mutate_or, r=alexcrichton

This implements parts of the changes to `Option` I proposed and discussed in this thread: https://mail.mozilla.org/pipermail/rust-dev/2013-November/006254.html, and on IRC.

In short, the string "default" should not be used in any context that has nothing to do with the `std::default::Default` trait.

This PR consists of this change:
- Renamed `map_default -> map_or` and `mutate_default -> mutate_or_set`.
Inline reexports in rustdoc

If a reexport comes from a non-public module, then the documentation for the
reexport will be inlined into the module that exports it, but if the reexport is
targeted at a public type (like the prelude), then it is not inlined but rather
hyperlinked.
auto merge of #11391 : alexcrichton/rust/rustdoc-inline, r=brson

If a reexport comes from a non-public module, then the documentation for the
reexport will be inlined into the module that exports it, but if the reexport is
targeted at a public type (like the prelude), then it is not inlined but rather
hyperlinked.
auto merge of #11358 : pcwalton/rust/typed-arenas, r=alexcrichton

A typed arena is a type of arena that can only allocate objects of one
type. It is 3x faster than the existing arena and 13x faster than malloc
on Mac.

r? @brson
auto merge of #11405 : huonw/rust/moredocs, r=huonw

Various documentation changes, change the 'borrowed pointer' terminology to 'reference', fix a problem with 'make dist' on windows.
Fix the snapshot and cross compilation

If we bootstrap a cross compile from a stage1 compiler, then the stage1 compiler
already knows about the rustc => rustlib change, so we need to not add the extra
flag if it's a stage0 version of a target from a stage1 of another target.
auto merge of #11407 : alexcrichton/rust/fix-snap, r=brson

If we bootstrap a cross compile from a stage1 compiler, then the stage1 compiler
already knows about the rustc => rustlib change, so we need to not add the extra
flag if it's a stage0 version of a target from a stage1 of another target.