Remove mach_sty
Remove codes related to modes
Convert most of rust_run_program.cpp to rust (issue #2674).
Remove errant trailing whitespace.
Add test for drop for newtype structs.
Fix some issues with test_destroy_actually_kills:
- it is now cross platform, instead of just unix
- it now avoids sleeping (fixing issue #6156)
- it now calls force_destroy() when force = true (was a bug)
libstd: De-mut arena
librustc: Update the serializer to work properly with INHTWAMA, removing mutable fields in the process
auto merge of #6195 : luqmana/rust/newtype-drop, r=catamorphism

Follow up with test case for #6125.
librustc: Make uninhabited enums not castable to int
auto merge of #6140 : Dretch/rust/run-with-rust, r=brson

Even more of `core::run` could be rust-ified -- I believe that access to the C extern environ can be done with rust now. I did not do this because some special casing is needed for OSX and I don't have a mac I can test with.

I think this will also fix #6096.
auto merge of #6201 : pcwalton/rust/inhtwama-serializer, r=graydon

This PR removes mutable fields from the serializer and makes the encoder and decoder use INHTWAMA properly (i.e. `&mut self`).

r? @graydon
auto merge of #6206 : sanxiyn/rust/mach-sty, r=thestinger
std: xfail test_serializing_pipes
auto merge of #6212 : brson/rust/xfail-flatpipes, r=brson

This is preventing a snapshot. Filed #6211
auto merge of #6204 : pcwalton/rust/uninhabited-enum-cast, r=catamorphism

r? @catamorphism
auto merge of #6207 : sanxiyn/rust/tc-big, r=thestinger