Auto merge of #21619 - brson:featureck-tidy, r=alexcrichton

Builds on my [feature staging PR](https://github.com/rust-lang/rust/pull/21248) to clean up the tidy scripts a bit, and make them much faster (6s vs ~40s).

Adds make rules 'tidy-basic', 'tidy-binaries', 'tidy-errors' and 'tidy-features'.

This is the output of `make tidy` here:

```
cfg: version 1.0.0-dev (a8c878d41 2015-01-25 01:49:14 -0800)
cfg: build triple x86_64-unknown-linux-gnu
cfg: host triples x86_64-unknown-linux-gnu
cfg: target triples x86_64-unknown-linux-gnu
cfg: host for x86_64-unknown-linux-gnu is x86_64
cfg: os for x86_64-unknown-linux-gnu is unknown-linux-gnu
cfg: good valgrind for x86_64-unknown-linux-gnu is 1
cfg: using CC=gcc (CFG_CC)
cfg: enabling valgrind run-pass tests (CFG_ENABLE_VALGRIND_RPASS)
cfg: valgrind-rpass command set to "/usr/bin/valgrind" --error-exitcode=100 --soname-synonyms=somalloc=NONE --quiet --suppressions=/home/brian/dev/rust3/src/etc/x86.supp  --tool=memcheck --leak-check=full
cfg: no lualatex found, deferring to xelatex
cfg: no xelatex found, deferring to pdflatex
cfg: no pdflatex found, disabling LaTeX docs
cfg: no pandoc found, omitting PDF and EPUB docs
cfg: including test rules
cfg: javac not available, skipping lexer test...
check: formatting

* linted .rs files: 4948
* linted .py files: 27
* linted .js files: 2
* linted .sh files: 5
* linted .pl files: 0
* linted .c files: 28
* linted .h files: 3
* other linted files: 0
* total lines of code: 481217
* total non-blank lines of code: 423682

check: binaries
check: extended errors

* 249 error codes
* highest error code: E0315

check: feature sanity

* advanced_slice_patterns         lang    unstable    None
* alloc                           lib     unstable    None
* asm                             lang    unstable    None
* associated_types                lang    stable      1.0.0
* box_syntax                      lang    unstable    None
* collections                     lib     unstable    None
* concat_idents                   lang    unstable    None
* core                            lib     unstable    None
* default_type_params             lang    stable      1.0.0
* globs                           lang    stable      1.0.0
* hash                            lib     unstable    None
* if_let                          lang    stable      1.0.0
* import_shadowing                lang    unstable    None
* int_uint                        lang    unstable    None
* intrinsics                      lang    unstable    None
* io                              lib     unstable    None
* issue_5723_bootstrap            lang    stable      1.0.0
* lang_items                      lang    unstable    None
* link_args                       lang    unstable    None
* link_llvm_intrinsics            lang    unstable    None
* linkage                         lang    unstable    None
* log_syntax                      lang    unstable    None
* macro_rules                     lang    stable      1.0.0
* main                            lang    unstable    None
* managed_boxes                   lang    unstable    None
* non_ascii_idents                lang    unstable    None
* old_impl_check                  lang    unstable    None
* old_orphan_check                lang    unstable    None
* on_unimplemented                lang    unstable    None
* opt_out_copy                    lang    unstable    None
* optin_builtin_traits            lang    unstable    None
* os                              lib     unstable    None
* path                            lib     unstable    None
* phase                           lang    unstable    None
* plugin                          lang    unstable    None
* plugin_registrar                lang    unstable    None
* quad_precision_float            lang    unstable    None
* quote                           lang    unstable    None
* rand                            lib     unstable    None
* rust1                           lib     stable      1.0.0
* rustc_diagnostic_macros         lang    unstable    None
* rustc_private                   lib     unstable    None
* rustdoc                         lib     unstable    None
* simd                            lang    unstable    None
* simd_ffi                        lang    unstable    None
* slicing_syntax                  lang    unstable    None
* staged_api                      lang    unstable    None
* start                           lang    unstable    None
* std_misc                        lib     unstable    None
* struct_inherit                  lang    unstable    None
* struct_variant                  lang    stable      1.0.0
* test                            lib     unstable    None
* test_accepted_feature           lang    stable      1.0.0
* test_removed_feature            lang    unstable    None
* thread_local                    lang    unstable    None
* trace_macros                    lang    unstable    None
* tuple_indexing                  lang    stable      1.0.0
* unboxed_closures                lang    unstable    None
* unicode                         lib     unstable    None
* unsafe_destructor               lang    unstable    None
* visible_private_types           lang    unstable    None
* while_let                       lang    stable      1.0.0
```

There's a lot of informational output now, which comes after things like 'NOTE's.