Add new lint: non_uppercase_pattern_statics, for #7526.

This tries to warn about code like:
    ```rust
    match (0,0) {
        (0, aha) => { ... },
        ...
    }
    ```
where `aha` is actually a static constant, not a binding.
Throwing in another interesting test case: There is no need to warn
about constants that are (non-trivial) paths rather than just
identifiers, regardless of what case their characters are.
Fix typo in comment.
Expanded test to clarify that the constants *are* matching when they should.
Workaround conflict between all-uppercase static and NaN definition.
Revise error message to use phrase "all caps" instead of "uppercase".

This is to clarify that the lint is checking for THIS_THING and not This.
make small (<= size_of::<int>()) tuples immediate

    fn foo() -> (u32, u8, u8, u8, u8) {
        (4, 5, 6, 7, 8)
    }

Before:

    ; Function Attrs: nounwind uwtable
    define void @_ZN3foo18hbb616262f874f8daf4v0.0E({ i32, i8, i8, i8, i8 }* noalias nocapture sret, { i64, %tydesc*, i8*, i8*, i8 }* nocapture readnone) #0 {
    "function top level":
      %2 = getelementptr inbounds { i32, i8, i8, i8, i8 }* %0, i64 0, i32 0
      store i32 4, i32* %2, align 4
      %3 = getelementptr inbounds { i32, i8, i8, i8, i8 }* %0, i64 0, i32 1
      store i8 5, i8* %3, align 4
      %4 = getelementptr inbounds { i32, i8, i8, i8, i8 }* %0, i64 0, i32 2
      store i8 6, i8* %4, align 1
      %5 = getelementptr inbounds { i32, i8, i8, i8, i8 }* %0, i64 0, i32 3
      store i8 7, i8* %5, align 2
      %6 = getelementptr inbounds { i32, i8, i8, i8, i8 }* %0, i64 0, i32 4
      store i8 8, i8* %6, align 1
      ret void
    }

After:

    ; Function Attrs: nounwind readnone uwtable
    define { i32, i8, i8, i8, i8 } @_ZN3foo18hbb616262f874f8daf4v0.0E({ i64, %tydesc*, i8*, i8*, i8 }* nocapture readnone) #0 {
    "function top level":
      ret { i32, i8, i8, i8, i8 } { i32 4, i8 5, i8 6, i8 7, i8 8 }
    }
fix tests for check-fast.
fix tests for check-fast.
incoporate suggestion from huonw to move code into lint.rs
Register new snapshots
Obsolete parsing 'loop' as 'continue'
Migrate users of 'loop' to 'continue'

Closes #9467
auto merge of #9656 : thestinger/rust/immediate, r=alexcrichton

    fn foo() -> (u32, u8, u8, u8, u8) {
        (4, 5, 6, 7, 8)
    }

Before:

    ; Function Attrs: nounwind uwtable
    define void @_ZN3foo18hbb616262f874f8daf4v0.0E({ i32, i8, i8, i8, i8 }* noalias nocapture sret, { i64, %tydesc*, i8*, i8*, i8 }* nocapture readnone) #0 {
    "function top level":
      %2 = getelementptr inbounds { i32, i8, i8, i8, i8 }* %0, i64 0, i32 0
      store i32 4, i32* %2, align 4
      %3 = getelementptr inbounds { i32, i8, i8, i8, i8 }* %0, i64 0, i32 1
      store i8 5, i8* %3, align 4
      %4 = getelementptr inbounds { i32, i8, i8, i8, i8 }* %0, i64 0, i32 2
      store i8 6, i8* %4, align 1
      %5 = getelementptr inbounds { i32, i8, i8, i8, i8 }* %0, i64 0, i32 3
      store i8 7, i8* %5, align 2
      %6 = getelementptr inbounds { i32, i8, i8, i8, i8 }* %0, i64 0, i32 4
      store i8 8, i8* %6, align 1
      ret void
    }

After:

    ; Function Attrs: nounwind readnone uwtable
    define { i32, i8, i8, i8, i8 } @_ZN3foo18hbb616262f874f8daf4v0.0E({ i64, %tydesc*, i8*, i8*, i8 }* nocapture readnone) #0 {
    "function top level":
      ret { i32, i8, i8, i8, i8 } { i32 4, i8 5, i8 6, i8 7, i8 8 }
    }
auto merge of #9638 : pnkfelix/rust/fsk-issue7526-attempt-to-catch-nonuc-statics-in-match-patterns, r=alexcrichton

r? anyone

Address scariest part of #7526 by adding a new more specific lint (that is set to warn by default, rather than allow).
auto merge of #9665 : alexcrichton/rust/snapshot, r=brson

Uses the new snapshots to kill the old `loop` and introduce the new `continue`.