make ty_region give a useful span when it fails
Miscellaneous documentation additions.

Added notes explaining how [expr, ..expr] form is used, targeted at
individuals like me who thought it was more general and handled
dynamic repeat expressions.  (I left a TODO for this section in a
comment, but perhaps that is bad form for the manual...)

Added example of `do` syntax with a function of arity > 1; yes, one
should be able to derive this from the text above it, but it is still
a useful detail to compare and contrast against the arity == 1 case.

Added example of using for expression over a uint range, since someone
who is most used to write `for(int i; i < lim; i++) { ... }` will
likely want to know how to translate that form (regardless of whether
it happens to be good style or not for their use-case).

Added note about the semi-strange meaning of "fixed size" of vectors
in the vector type section.
Fixes mozilla/rust#3612.
Spelling fixes; replaced `size` with `capacity` in few places.
Cleanup wording around the awkward "and so on is . ." in the README.txt.
Updated to reflect alpha-rename of constant/static items section.
auto merge of #5546 : nikomatsakis/rust/ty_region-useful-span, r=catamorphism

r? @catamorphism
auto merge of #5553 : pnkfelix/rust/doc-fixes-for-0.6-incoming, r=sanxiyn
rustdoc: Sanitize links harder
rustdoc: Build the crate config correctly. Fixes #5011
rustdoc: Handle impl method visibility correctly. #5533
rustdoc: Add type bounds to impls
rustdoc: Tweak list style
Fix #4855: handle bot in regionck
Check for null in return_to_mut.  Fixes #4904.
Remove unused imports throughout
syntax: Removing uses of HashMap
doc: Remove mentions of oldmap::HashMap
rustc: Remove uses of oldmap::HashMap
rustc: Purge of HashMap, fixing segfaulting cases

Various XXX comments added around to denote copies which when removed cause the
compiler to segfault at some point before stage2. None of these copies should
even be necessary.