[flang] Merge pull request flang-compiler/f18#539 from flang-compiler/tsk1

Check that procedures of a generic are distinguishable

Original-commit: flang-compiler/f18@a24701e313019dbf84179b79e234f92d61de0fa6
Reviewed-on: https://github.com/flang-compiler/f18/pull/539

Due to a conflicting rebase during the linearizing of flang-compiler/f18, this commit squashes a number of other commits:

flang-compiler/f18@9b1343af36bd27b110f31dab39c3a18a657a5760 Some cleanup in characteristics.{h,cc}
flang-compiler/f18@ddb70e53d2b4e2bba12686e4ac3c26052758fcc3 Merge branch 'master' of github.com:flang-compiler/f18 into tsk1
flang-compiler/f18@d1eef9506610a427f992180f6b59cafe09abb9b9 Merge branch 'master' of github.com:flang-compiler/f18 into tsk1
flang-compiler/f18@24a6d3ffbf4d26d92222b27faa155bb5b3f517f4 Make test_folding.sh stricter in test for warnings
flang-compiler/f18@c2c5b640604acceb45823de8cb5716d6921da7d4 Replace SymbolList with SymbolVector
flang-compiler/f18@c8499584dff12381c2ce6d4718761cd225b4d97a Add CopyAttrs to copy attributes from Symbol
flang-compiler/f18@0573ffd8b2ed5757e06a4fc6d5ffc4401e800c32 Replace cascading detailsIf calls with std::visit
flang-compiler/f18@28ec62b3ffeec1d25fde330069b050655bb52a5d Add name to characteristics::DummyArgument
flang-compiler/f18@568eaf01145d4ee979423d06f2a65d07222f6841 Add name to CopySymbol()
flang-compiler/f18@8c557b09e752da205cd300f63b5ca69806fb2e78 Check that procedures of a generic are distinguishable
flang-compiler/f18@50515fd987fd5479567e1b497f6ba93974ffde76 Merge branch 'master' of github.com:flang-compiler/f18 into tsk1
flang-compiler/f18@a7963e98a4aedc97784b99903d04cdc48fd4c346 Address review comments
flang-compiler/f18@edd65b3962dbaa1121c166d47c90730e39c25a04 Merge branch 'master' of github.com:flang-compiler/f18 into tsk1