submodules: update clippy from b1d03437 to 3971c424

[matthiaskrgr]

Should make clippy tests green again on rust-toolstate

Changes:

compiletest: clean rmeta data (from "cargo check") before running compiletest.
dependencies: bump compiletest-rs from git to 0.3.16
UI test cleanup: Extract explicit_counter_loop tests
UI test cleanup: Extract unnecessary_operation tests
appveyor: use rustc nightly instead of master
pin compiletest dependency to git version (12c980f47971b5ba6beb7cb2ffebf8b32f6766ea) while we are waiting for a new release
rustup: fix build with rustc 1.31.0-nightly (cae6efc37 2018-10-27)
Disable rust master toolchain build temporarily
Don't expand macro in or_fun_call suggestion
Don't expand macro in single_match suggestion
Don't expand macro in identity_conversion suggestion
slightly simplify integration tests
simplify ci base-tests
fix: correctly reconstruct raw strings
fix: extra semicolon, only create callsite once
Fix string_lit_as_bytes lint for macros
travis: work around temporary test failure due to rustc crashing on hyper.
ci: allow all branches except trying.tmp and staging.tmp to be built
Move in_macro check
Use BasicBlockData::terminator
Refactor
Use lint_root
Implement visit_basic_block_data
update_references indexing_slicing
Run update_lints
Add redundant_clone lint
Revert "new_ret_no_self: add sample from #3313 to Known Problems section."
Add tests for more than one level of reference
Add test case for `mem::discriminant` inside a macro
Add `Applicability`
Add lint for calling `mem::discriminant` on a non-enum type
Check existential types in `use_self`
Disable arithmetic lints in constant items
Fix warnings introduced by #3349
new_ret_no_self added test cases
Replace remaining `krate.span` with `DUMMY_SP`
Use DUMMY_SP in multiple_crate_versions
Some fixes for wildcard_dependencies
Run util/update_lints.py
Minor changes on clippy_lints/src/wildcard_dependencies.rs
Lint for wildcard dependencies in Cargo.toml
Don't emit `new_without_default_derive` if an impl of Default exists
Fix inspector pass documentation
Add branch configuration to appveyor.yml
Setup bors
new_ret_no_self added test cases
new_ret_no_self walk return type to check for self
Update `ui/for_loop` test output
Check for known array length in `needless_range_loop`
new_ret_no_self correct false positive on raw pointer return types
new_ret_no_self correct linting of tuple return types
out_of_bounds_indexing improved reporting of out of bounds value
out_of_bounds_indexing refactoring
OUT_OF_BOUNDS_INDEXING fix #3102 false negative

[rust-highfive]

r? @aturon

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[rust-highfive]

⚠️ Warning ⚠️

• These commits modify submodules.

[kennytm]

🤔 There is also #55496 and already r+'ed

[matthiaskrgr]

Oh well...