auto merge of #12177 : alexcrichton/rust/fix-snapshot, r=kballard

This is blocking a snapshot because the stage0 target compiler comes from a
stage1 host compiler. This means that the stage0 compiler doesn't actually
understand the -Z prefer-dynamic flag and is dying as a result.

This will get added back to stage0 after a snapshot.
 Explain container iteration in the loop tutorial

 As suggested by @pnkfelix in #12161, this extends the examples by a for-loop
 that iterates over a string as an example for container iteration.
Fix broken link to the container guide
remove dead link to rustpkg documentation
auto merge of #12181 : sanxiyn/rust/accurate-span-4, r=alexcrichton
Tweak test name and make it more specific
Change `xfail` directives in compiletests to `ignore`, closes #11363
auto merge of #12110 : fhahn/rust/issue-11363-change-xfail, r=alexcrichton

Patch for #11363
Add ignore-cross-compile directive for compiletest

Loadable syntax extensions don't work when cross compiling (see #12102), so the
fourcc tests all need to be ignored. They're valuable tests, so they shouldn't
be outright ignored, so they're now flagged with ignore-cross-compile
auto merge of #12171 : chromatic/rust/fix_crate_tutorial_typos, r=brson

This commit attempts to clarify a section of the tutorial. It also fixes some typos.
Includes new add method that uses .clone() for support.

Added new tests for bsearch methods and changed "add" to "insert"

Fixed failure on div_floor.
auto merge of #12183 : SimonSapin/rust/patch-4, r=alexcrichton
std -- replaces uses where const borrows would be required
remove antiquated reflect test rather than bring it up to date
libglob -- patch closure where const borrow would have helped
container -- update example to contain scope of closure borrow
to_str -- update to contain scope of closure
ty -- minor refactorings, helper methods
trans/datum -- move mutable variable into closure
error_reporting -- explain reborrowed upvar constraints in a hopefully useful way