Issue 974 in include-what-you-use: Please make a release compatible with llvm-13.0.0

[notifi...@include-what-you-use.org]

New issue 974 by 0-wiz-0: Please make a release compatible with llvm-13.0.0
https://github.com/include-what-you-use/include-what-you-use/issues/974

The build of 0.16 fails with
```
/scratch/devel/include-what-you-use/work/include-what-you-use/iwyu.cc: In member function 'void include_what_you_use::IwyuBaseAstVisitor<Derived>::Add
ShadowDeclarations(const clang::UsingDecl*)':
/scratch/devel/include-what-you-use/work/include-what-you-use/iwyu.cc:2649:54: error: 'const class clang::UsingShadowDecl' has no member named 'getUsi
ngDecl'
2649 | make_pair(shadow->getTargetDecl(), shadow->getUsingDecl()));
| ^~~~~~~~~~~~
/scratch/devel/include-what-you-use/work/include-what-you-use/iwyu.cc: In member function 'const clang::UsingDecl* include_what_you_use::IwyuBaseAstVi
sitor<Derived>::GetUsingDeclarationOf(const clang::NamedDecl*, const clang::DeclContext*)':
/scratch/devel/include-what-you-use/work/include-what-you-use/iwyu.cc:2669:22: error: 'const class clang::UsingShadowDecl' has no member named 'getUsi
ngDecl'
2669 | return shadow->getUsingDecl();
| ^~~~~~~~~~~~
```
the code seems to have been modified in the git repository in the meantime, but there is no new release, which would be very handy for packagers.
Thank you!

[notifi...@include-what-you-use.org]

Comment #0 on issue 974 by kimgr: Please make a release compatible with llvm-13.0.0
https://github.com/include-what-you-use/include-what-you-use/issues/974

I have been meaning to get this done, but I've been busy the past month. Just to let you know that I'm not ignoring this, I'll get to it as soon as I can.