Spawn new tasks onto the primary scheduler by default. #3760
Add at_exit function #4450
core: Add private global data interface. #3915
Add `finally` method for deferred execution
core: Add new weak task API
core: Convert getenv/setenv to use a mutex

This much simpler implementation uses a global mutex
and eliminates the kernel environment channel.
std: Convert uv_global_loop to use pipes
core: Remove private::chan_from_global_ptr. #3915
Remove old comm-based weak task interface
core: Stop using oldcomm
unit test cases now pass, added a few to the interner
Merge pull request #4617 from jbclements/libsyntax-tests-now-pass

unit test cases now pass, added a few to the interner
rustc: One Less Bad Copy
remove support for records from auto_encode
convert most of libcore records into structs
core: convert io::Res over to the Drop trait
Remove "unsafe" from run::start_program
convert most of libstd over to structs
time tests are racing on tzset, so merge the tests together.

This attempts to fix issue #3327.
Fix a typo