Revert r247218: "Fix Clang-tidy misc-use-override warnings, other minor fixes"

Seems it broke the Polly build.
From http://lab.llvm.org:8011/builders/perf-x86_64-penryn-O3-polly-fast/builds/11687/steps/compile/logs/stdio:

In file included from /home/grosser/buildslave/perf-x86_64-penryn-O3-polly-fast/llvm.src/lib/TableGen/Record.cpp:14:0:
/home/grosser/buildslave/perf-x86_64-penryn-O3-polly-fast/llvm.src/include/llvm/TableGen/Record.h:369:3: error: looser throw specifier for 'virtual llvm::TypedInit::~TypedInit()'
/home/grosser/buildslave/perf-x86_64-penryn-O3-polly-fast/llvm.src/include/llvm/TableGen/Record.h:270:11: error:   overriding 'virtual llvm::Init::~Init() noexcept (true)'

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@247222 91177308-0d34-0410-b5e6-96231b3b80d8