Add draft 0.10 release notes
dist: Add libbacktrace to source tarballs
mk: distcheck --uninstall
mk: Workaround distcheck failure on mac. #13224

Mac can't actually build our source tarballs because it's `tar`
command doesn't support the --exclude-vcs flag. This is just
a workaround to make our mac nightlies work (we get our source
tarballs from the linux bot).
auto merge of #13223 : brson/rust/dist, r=alexcrichton
Json doesn't need to depend on IoError to implement Encodable #13230
auto merge of #13230 : Kroisse/rust/encodable-json, r=erickt

The implementation of `Encodable<E, S>` for `Json` doesn't need to assume `S` to be `IoError`, only the default encoders for `Json` are depend on it. So this can be parametrize to increase flexiblity. If not, types that implement `Encoder<E>` where `E` is not `IoError` can't be worked with `Json`.
auto merge of #13189 : alexcrichton/rust/relnotes, r=brson
rustc: Switch struct fields to private by default

This commit switches privacy's checking of fields to have *all* fields be
private by default. This does not yet change tuple structs, this only affects
structs with named fields. The fallout of this change will follow shortly.

RFC: 0004-private-fields

cc #8122
Closes #11809
Bump version to 0.10
num: rm wrapping of `Float` methods as functions

The `Float` trait methods will be usable as functions via UFCS, and
we came to a consensus to remove duplicate functions like this a long
time ago.

It does still make sense to keep the duplicate functions when the trait
methods are static, unless the decision to leave out the in-scope trait
name resolution for static methods changes.
std: Switch field privacy as necessary
collections: Switch field privacy as necessary
getopts: Switch field privacy as necessary
native: Switch field privacy as necessary
rand: Switch field privacy as necessary
sync: Switch field privacy as necessary
arena: Switch field privacy as necessary
log: Swith field privacy as necessary
serialize: Switch field privacy as necessary