Revised Crate section of tutorial for clarity.
Fix broken link to the container guide
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.
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
metadata -- remove tiny convenience closure that was causing conflicting mutable borrows
resolve -- rewrite conflict closure into method
syntax/ext/format -- rewrite conflicting closures into methods
syntax/fold -- remove conflicting (and rather pointless) closures
vec -- introduce local var to make clear what subportion is being borrowed
back/link -- introduce block to clarify scope of closure
ppaux -- add Repr implementations
io -- introduce local to avoid conflicting borrow