extra: Remove dbg module and rt support code

This stuff is ancient, unused, and tied to oldsched
Resolve globals having different addresses across crates

* All globals marked as `pub` won't have the `internal` linkage type set
* All global references across crates are forced to use the address of the
  global in the other crate via an external reference.
auto merge of #8185 : alexcrichton/rust/issue-8179, r=pcwalton

* All globals marked as `pub` won't have the `internal` linkage type set
* All global references across crates are forced to use the address of the
  global in the other crate via an external reference.

r? @graydon

Closes #8179
replace `range` with an external iterator
auto merge of #8216 : thestinger/rust/range, r=huonw
auto merge of #8175 : brson/rust/nodbg, r=graydon

This stuff is ancient, unused, and tied to oldsched