use option_env! instead of env!
Pre-step towards issue #12624 and others: Introduce ExprUseVisitor, remove the
moves computation. ExprUseVisitor is a visitor that walks the AST for a
function and calls a delegate to inform it where borrows, copies, and moves
occur.

In this patch, I rewrite the gather_loans visitor to use ExprUseVisitor, but in
future patches, I think we could rewrite regionck, check_loans, and possibly
other passes to use it as well. This would refactor the repeated code between
those places that tries to determine where copies/moves/etc occur.
Convert delegate to use an object type and remove FIXME from closed issue
rustdoc: refactor and unstyle inline section headers
doc: perform some 80-chars wrappings
syntax: `Mod` records the span for inner contents.

this is useful when the module item and module contents are defined
from different files (like rustdoc). in most cases the original span
for the module item would be used; in other cases, the span for
module contents is available separately at the `inner` field.
test: Rename a test to bypass UAC on windows
rustdoc: style tweaks
rustdoc: External module item links to the module contents. Fixes #12926.

the basic strategy is to distinguish `mod foo;` from `mod foo {...}`
by checking if the span for the module item and module contents is
in different files. if it's the case, we prefer module contents.

it is technically possible to fix #12926 without changing the AST,
probably by checking the individual items' span. this is not without
a problem though, since it is possible that some items inside
`mod foo {...}` may have originated from other file (e.g. `include!`).
therefore it is better to record both spans explicitly.
Fix link to hashmap.rs and json.rs in sample code FAQ
Added missing values in std::io::standard_error()
add BigUint subtraction underflow error message
auto merge of #13796 : ema-fox/rust/patch-1, r=kballard
auto merge of #13798 : aochagavia/rust/pr, r=alexcrichton
Rewrote documentation for parse_bytes and to_str_bytes in {int, uint}_macros.rs
Add a streaming parser to serialize::json.
Fix a code formatting issue in json.rs
Update libworkcache with libserialize's json changes
Fix test issue-4016.rs with the json API change
auto merge of #13792 : jacob-hegna/rust/master, r=alexcrichton

Just modified the documentation for parse_bytes to make it more clear how the bytes were parsed (big endian) and to show an example of what it returned.  I also added documentation for the to_str_bytes which previously had no documentation (besides one stackoverflow post).