Fixed os:: and int:: not being in scope, changed io::println to println
Updated copyright year on shootout-binarytrees.rs
Changed shootout-chameneos-redux output to conform to the 'official' output format.
Added missing copyright notice to shootout-spectralnorm.
Fixed shootout-fasta.rs output
Updated shootout-fasta.rs copyright years, removed stuff that caused lint to complain.
Changed Arena API to make it usable once more.
auto merge of #7193 : Thiez/rust/fixbench, r=cmr

This PR fixes a few problems with the benchmark, mentioned in #2913. Since I do not have a 4GB RAM machine (I run rust on a puny 2GB RAM VM) I can't test binarytrees with N=20. If it works we can close #2913.

Fixes: 1) binarytrees prints "long lived trees of depth" instead of "long lived tree of depth"
Fixes: 2) chameneosredux -- the whitespace printed by show_number should be the same as printed by show_color
Already fixed: 3) spectralnorm prints an extra 

Fixes: 4) threadring prints an extra 

Fixes: 5) fasta -- strangely, output stops half-way through line 169 -- with another 8166 lines still to do.
Could not test: 6) the latest binarytrees fails with input N=20 on a 4GB machine.

r?
Update existing tests to account for stricter, more correct handling of irrefutable patterns
Add new tests for irrefutable patterns used in various tricky ways
update ptr intrinsics and rewrite vec routines to be more correct.

In particular, it is not valid to go around passing uninitialized or zero'd
memory as arguments. Rust should generally be free to assume that the arguments
it gets are valid input values, but the output of intrinsics::uninit() and
intrinsics::init() are not (e.g., an @T is just null, leading to an error
if we should try to increment the ref count).
Patch up some code that was using irrefutable patterns incorrectly.
syntax: Patch up code that was using irrefutable patterns incorrectly
extra: Patch up code that was using irrefutable patterns incorrectly.
Make all allocas named so we can see where they originate
in the generated LLVM code.
Update trans to use type to decide when to move, not the moves table (simpler
for cases where it's hard to decide what id to use for the lookup); modify
irrefutable bindings code to move or copy depending on the type, rather than
threading through a flag. Also updates how local variables and arguments are
registered. These changes were hard to isolate.
Modify borrow checker to visit irrefutable patterns that appear in
let and function arguments; modify type checker to store type
information for all patterns and handles some missing cases.
Miscellaneous fixes and cleanup
This assert does not necessarily hold; sometimes we temporarily increase ref-count
Address nits by @catamorphism