librustc: Don't ICE with type when name only contain underscores.
lint: Improve camel case suggestion when empty.
auto merge of #16704 : flugsio/rust/fix-rustc-ice-lint-underscores-only, r=brson

Fix for type identifiers with only underscores (two or more), I assume they doesn't count as camel case.

```rust
type __ = int;

fn main() {
}
```

```
error: internal compiler error: unexpected failure
note: the compiler hit an unexpected failure path. this is a bug.
note: we would appreciate a bug report: http://doc.rust-lang.org/complement-bugreport.html
note: run with `RUST_BACKTRACE=1` for a backtrace
task 'rustc' failed at 'index out of bounds: the len is 0 but the index is 0', /home/rustbuild/src/rust-buildbot/slave/nightly-linux/build/src/librustc/lib.rs:1

stack backtrace:
   1: 0xb603f5d0 - rt::backtrace::imp::write::ha55f265f6626471dmxr
   2: 0xb6042620 - failure::on_fail::h4d2c6d42b67e94803Sr
   3: 0xb640a180 - unwind::begin_unwind_inner::h484879fa7cc3611fZhe
   4: 0xb6409e50 - unwind::begin_unwind_fmt::hd14e5c64bc9006capfe
   5: 0xb6409df0 - rust_begin_unwind
   6: 0xb6454580 - failure::begin_unwind::h9ab1fc5753bd08f3YDk
   7: 0xb6458cb0 - failure::fail_bounds_check::h88167bad36865909aCk
   8: 0xb6f685d0 - lint::builtin::NonCamelCaseTypes.LintPass::check_item::check_case::he854eeffd105cb0f40E
   9: 0xb6f68050 - lint::builtin::NonCamelCaseTypes.LintPass::check_item::hc35b45d248e41cd43XE
  10: 0xb6f7b760 - lint::context::Context<'a>.Visitor<(*>::visit_item::closure.139262
  11: 0xb6f79510 - lint::context::Context<'a>::with_lint_attrs::hb9efe321fa321ce6spG
  12: 0xb6f81d30 - lint::context::Context<'a>.Visitor<(*>::visit_mod::he4593c831936b308ZMG
  13: 0xb6f8f2f0 - lint::context::check_crate::closure.139319
  14: 0xb6f79510 - lint::context::Context<'a>::with_lint_attrs::hb9efe321fa321ce6spG
  15: 0xb6efda70 - lint::context::check_crate::ha9e64328726b9579q1G
  16: 0xb6efda20 - driver::driver::phase_3_run_analysis_passes::closure.136263
  17: 0xb659d640 - util::common::time::h2837683151147173214
  18: 0xb6e7d130 - driver::driver::phase_3_run_analysis_passes::h7079eff53afc4de3Jfz
  19: 0xb6e783f0 - driver::driver::compile_input::h0ec84a550e24779cP1y
  20: 0xb6f26250 - driver::run_compiler::h7e7c01ecbfd0ad87JzC
  21: 0xb6f26150 - driver::main_args::closure.137215
  22: 0xb6f380d0 - task::TaskBuilder<S>::try_future::closure.138376
  23: 0xb6f37ec0 - task::TaskBuilder<S>::spawn_internal::closure.138353
  24: 0xb774bdd0 - task::spawn_opts::closure.8325
  25: 0xb6409c10 - unwind::try::try_fn::h91f00772748cf73eD8d
  26: 0xb6468ae0 - rust_try_inner
  27: 0xb6468aa0 - rust_try
  28: 0xb6407880 - unwind::try::h78a4fc0e85c326aef6d
  29: 0xb6407640 - task::Task::run::hb6f2d9484116e3d8xcd
  30: 0xb774bba0 - task::spawn_opts::closure.8271
  31: 0xb6409350 - thread::thread_start::h8c02fef9f651da5cjBd
  32: 0xb5ed3fc0 - start_thread
  33: 0xb62e8a32 - __clone
  34:        0x0 - <unknown>
```
glob: Deprecate the library in favor of cargo

This library has been moved out to a cargo package in rust-lang.
auto merge of #16685 : alexcrichton/rust/remove-glob, r=brson

This library has been moved out to a cargo package in rust-lang.
extern crate foobar as foo;

Implements remaining part of RFC #47.
Addresses issue #16461.

Removed link_attrs from rust.md, they don't appear to be supported by
the parser.

Changed all the tests to use the new extern crate syntax

Change pretty printer to use 'as' syntax
debuginfo: Allow to activate GDB pretty printers in autotests.
debuginfo: Add GDB pretty printers for structs and enums.
debuginfo: Emit different autotest debugger scripts depending on GDB version.
debuginfo: Allow debuginfo tests to be ignored based on GDB version.
debuginfo: Activate debuginfo tests in check-lite for try branch