num: implement CheckedDiv
port resolve.rs from oldvisit to <V:Visitor> trait.
Ported trans/base.rs from oldvisit to <V:Visitor> trait API.
Ported liveness.rs from oldvisit to <V:Visitor> trait API.
Ported typeck::collect from oldvisit to <V:Visitor> trait API.
port callee.rs from oldvisit to <V:Visitor> trait API.
port type_use.rs from oldvisit to <V:Visitor> trait.
Ported typeck/check/mod.rs from oldvisit to <V:Visitor> trait API.
port util/common.rs from oldvisit to <V:Visitor> trait API.
Ported coherence.rs from oldvisit to <V:Visitor> trait API.
Ported rusti::utils from oldvisit to <V:Visitor> trait API.
Port entry.rs from oldvisit to <V:Visitor> trait API.
Port freevars.rs from oldvisit to <V:Visitor> trait.
Port kind.rs from oldvisit to <V:Visitor> trait API.
ported lang_items from oldvisit to <V:Visitor> trait.
Port regionck from oldvisit to <V:Visitor> trait API.
Port check_loans.rs from oldvisit to <V:Visitor> trait API.
an attempt at a singleton pausible idle callback for each scheduler. suffers from nondeterministic deadlock and also pending scheduler messages on scheduler shutdown.
std::rt: Touch up idle logic
std::rt: Fix a race in UvRemoteCallback's dtor that misses callbacks

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