It is suffering from a bad case of megabitrot.

Currently, when calling glue functions, we cast the function to match
the argument type. This interacts very badly with LLVM and breaks
inlining of the glue code.

It's more efficient to use a unified function type for the glue
functions and always cast the function argument instead of the function.

The resulting code for rustc is about 13% faster (measured up to and
including the "trans" pass) and the resulting librustc is about 5%
smaller.

Currently, when calling glue functions, we cast the function to match
the argument type. This interacts very badly with LLVM and breaks
inlining of the glue code.

It's more efficient to use a unified function type for the glue
functions and always cast the function argument instead of the function.

The resulting code for rustc is about 13% faster (measured up to and
including the "trans" pass) and the resulting librustc is about 5%
smaller.

r? @graydon Automate more tests described in the commands.txt file,
and add infrastructure for running them. Right now, tests shell
out to call rustpkg. This is not ideal.

Goes part of the way towards addressing #5683

This is caused by StrVector having a generic implementation for &[S]
and so #5898 means that method resolution of ~[~[1]].concat() sees that
both StrVector and VectorVector have methods that (superficially) match.

They are now connect_vec and concat_vec, which means that they can actually be
called.

This means that type definitions and function signatures have
pretty colours.

r? @brson

links to issues: #7065 the race that's fixed; #7066 the perf improvement I added. There are also some minor cleanup commits here.

To measure the performance improvement from replacing the exclusive with an atomic uint, I edited the ```msgsend-ring-rw-arcs``` bench test to do a ```write_downgrade``` instead of just a ```write```, so that it stressed the code paths that accessed ```read_count```. (At first I was still using ```write``` and saw no performance difference whatsoever, whoooops.)

The bench test measures how long it takes to send 1,000,000 messages by using rwarcs to emulate pipes. I also measured the performance difference imposed by the fix to the ```access_lock``` race (which involves taking an extra semaphore in the ```cond.wait()``` path). The net result is that fixing the race imposes a 4% to 5% slowdown, but doing the atomic uint optimization gives a 6% to 8% speedup.

Note that this speedup will be most visible in read- or downgrade-heavy workloads. If an RWARC's only users are writers, the optimization doesn't matter. All the same, I think this more than justifies the extra complexity I mentioned in #7066.

The raw numbers are:
```
with xadd read count
        before write_cond fix
                4.18 to 4.26 us/message
        with write_cond fix
                4.35 to 4.39 us/message
                
with exclusive read count
        before write_cond fix
                4.41 to 4.47 us/message
        with write_cond fix
                4.65 to 4.76 us/message
```

Implement conditional support in terminfo, along with a few other related operators.

Fix implementation of non-commutative arithmetic operators.

Remove all known cases of task failure from `terminfo::parm::expand`, and change the method signature.

Fix some other miscellaneous issues.

This un-reverts the reverts of the rusti commits made awhile back. These were reverted for an LLVM failure in rustpkg. I believe that this is not a problem with these commits, but rather that rustc is being used in parallel for rustpkg tests (in-process). This is not working yet (almost! see #7011), so I serialized all the tests to run one after another.

@brson, I'm mainly just guessing as to the cause of the LLVM failures in rustpkg tests. I'm confident that running tests in parallel is more likely to be the problem than those commits I made.

Additionally, this fixes two recently reported issues with rusti.

Automate more tests described in the commands.txt file,
and add infrastructure for running them. Right now, tests shell
out to call rustpkg. This is not ideal.

This confused me when it happened.

r? @pnkfelix

This is caused by StrVector having a generic implementation for &[S]
and so #5898 means that method resolution of ~[~[1]].concat() sees that
both StrVector and VectorVector have methods that (superficially) match.

They are now connect_vec and concat_vec, which means that they can actually be
called.

The lookups for these items in external crates currently cause repeated
decoding of the EBML metadata, which is pretty slow. Adding caches to
avoid the repeated decoding reduces the time required for the type
checking of librustc by about 25%.

copies can just be done explicitly: `xs.transform(|x|x.clone())`

replaced with mutable implementations of Iterator

replaced with `xs.mut_iter().enumerate()`

The lookups for these items in external crates currently cause repeated
decoding of the EBML metadata, which is pretty slow. Adding caches to
avoid the repeated decoding reduces the time required for the type
checking of librustc by about 25%.

Implement the %?, %t, %e, and %; operators. Also implement the %<, %=,
%> operators, without which conditionals aren't very useful.

Fix the order of parameters for the arithmetic operators.

Implement the missing %^ operator.

Replace all potentially-failing operations with Err returns and add
tests.

Remove the Char parameter type; characters are represented as Numbers.

Fix integer constants to work properly when there are multiple constants
in the same capability string.

Tweak loop to use iterators instead of indexing into cap.

Take a new struct Variables instead of two &mut [] vectors for static
and dynamic variables.

This means that type definitions and function signatures have
pretty colours.

It uses the following template:

~~~ {.rust}
<code>
~~~

std: get std::path tests to work again

These passes are already run beforehand, no need to do them twice.

Closes #7120

This reverts commit 19adece6.

This reverts commit 541c657a.

This fixes the strange random crashes in compile-fail tests.

This reverts commit 96cd61ad.

Conflicts:
	src/librustc/driver/driver.rs
	src/libstd/str.rs
	src/libsyntax/ext/quote.rs