str: Add method .into_owned(self) -> ~str to Str

The method .into_owned() is meant to be used as an optimization when you
need to get a ~str from a Str, but don't want to unnecessarily copy it
if it's already a ~str.

This is meant to ease functions that look like

  fn foo<S: Str>(strs: &[S])

Previously they could work with the strings as slices using .as_slice(),
but producing ~str required copying the string, even if the vector
turned out be a &[~str] already.
Replace 'blk' -> 'block' in AstBuilder.

I didn't rename variables because they are local and are not parts of
the public interfaces.

Signed-off-by: OGINO Masanori <masanori.ogino@gmail.com>
Fix calling destructor on uninitialized dynamic library crash.

A test case was also created for this situation to prevent the problem
occuring again.

A similar problem was also fixed for the symbol method.

There was some minor code cleanup.
std: Speed up str::is_utf8

Use unchecked vec indexing since the vector bounds are checked by the
loop. Iterators are not easy to use in this case since we skip 1-4 bytes
each lap. This part of the commit speeds up is_utf8 for ASCII input.

Check codepoint ranges by checking the byte ranges manually instead of
computing a full decoding for multibyte encodings. This is easy to read
and corresponds to the UTF-8 syntax in the RFC.

No changes to what we accept. A comment notes that surrogate halves are
accepted.

Before:

	test str::bench::is_utf8_100_ascii ... bench: 165 ns/iter (+/- 3)
	test str::bench::is_utf8_100_multibyte ... bench: 218 ns/iter (+/- 5)

After:
	test str::bench::is_utf8_100_ascii ... bench: 130 ns/iter (+/- 1)
	test str::bench::is_utf8_100_multibyte ... bench: 156 ns/iter (+/- 3)
Add trait name to conflicting implementation error message
Add backticks around trait name in conflicting implementations error message
Rename IpAddr -> SocketAddr, extract IpAddr from SocketAddr

multicast functions now take IpAddr (without port), because they dont't
need port.

Uv* types renamed:
* UvIpAddr -> UvSocketAddr
* UvIpv4 -> UvIpv4SocketAddr
* UvIpv6 -> UvIpv6SocketAddr

"Socket address" is a common name for (ip-address, port) pair (e.g. in
sockaddr_in struct).
Sha2: Remove unecessary integer type specifications.
Sha2: Rearrage traits / impls / structs.

The code was arranged so that the core Sha2 code came first, and then
all of the various implementation of Digest followed along later. The
problem is that the Sha512 compression function code is far away from
the Sha512 Digest implementation, so, if you are trying to read over
the code, you need to scroll all around the file for no good reason. The
code was rearranged so that all of the Sha512 code is in one place and
all of the Sha256 code is in another and so that all impls for a struct
are near the definition of that struct.
Sha2: Remove the result_X() methods; move logic into the Digest impls.

The result_X() methods just calculate an output of a fixed size. They don't
really have much to do with running the actually hash algorithm until the very
last step - the output. It makes much more sense to put all this logic into
the Digest impls for each specific variation on the hash function.
Sha2: Create cryptoutil.rs and re-write the Sha2 module to make use of it.

There are 2 main pieces of functionality in cryptoutil.rs:
* A set of unsafe function for efficiently reading and writing u32 and u64
  values. All of these functions are fairly easy to audit to confirm that
  they do what they are supposed to.
* A FixedBuffer struct. This struct keeps track of input data until there
  is enough of it to execute the a function on it which expects a fixed
  block of data.

The Sha2 module was rewritten to take advantage of the new functions in
cryptoutil as well as FixedBuffer. The result is that the duplicate code
for maintaining a buffer of input data is removed from the Sha512 and
Sha256 implementation. Additionally, the FixedBuffer code is much more
efficient than the previous code was.
Sha2: Re-write the Sha2 compression functions to improve performance.

The Sha2 compression functions were re-written to execute the message
scheduling calculations in the same loop as the rest of the compression
function. The compiler is able to generate much better code. Additionally,
innermost part of the compression functions were turned into macros to
reduce code duplicate and to make the functions more concise.
Crypto: Remove DigestUtil and convert to default methods on the Digest trait.
Crypto: Add large input tests for all Digests

Create a helper function in cryptoutil.rs which feeds 1,000,000 'a's into
a Digest with varying input sizes and then checks the result. This is
essentially the same as one of Sha1's existing tests, so, that test was
re-implemented using this method. New tests were added using this method for
Sha512 and Sha256.
Crypto: Add overflow checking addition functions.

Added functions to cryptoutil.rs that perform an addition after shifting
the 2nd parameter by a specified constant. These function fail!() if integer
overflow will result. Updated the Sha2 implementation to use these functions.
Sha1: Update Sha1 to use new functionality in cryptoutil.rs
Add default implementation of Map::contains_key function

Map::contains_key can be implemented with Map::find.

Remove several implementations of contains_key.
auto merge of #8174 : DaGenix/rust/digest-improvements, r=brson

Same content as #8097, but bors had an issue with that pull request. Opening a new one.
Revert "std::rt: Use a constant 4 threads for multithreaded sched tests"

This workaround was less than ideal. A better solution is to raise the
fd limit.

This reverts commit 49b72bdd77916e27aaf95909516702c1450f11ac.
Bump fd limit on macos when running rt tests

OS X defaults the ulimit for open files to 256 for programs launched
from the Terminal (GUI apps get a higher default). Unfortunately this is
too low for the rt tests, which deliberately overcommit and create a lot
of threads (which means a lot of schedulers, and each scheduler needs at
least 2 fds).

By calling sysctl() and setrlimit() we can bump the fd limit up to the
maximum allowed (on stock OS X it's 10240).

Fixes #7772.