ghc::filesystem Release v1.5.6

Changes:

• Fix for #124, ghc::filesystem treated mounted folder/volumes erroneously as symlinks, leading fs::canonical to fail on paths containing those.
• Fix for #122, incrementing the recursive_directory_iterator will not try to enter dead symlinks.
• Fix for #121, on Windows backend the fs::remove failed when the path pointed to a read-only entry, see also (microsoft/STL#1511) for the corresponding issue in std::fs on windows.
• Fix for #119, added missing support for char16_t and char32_t and on C++20 char8_t literals.
• Pull request #118, when running tests as root, disable tests that would not work.
• Pull request #117, added checks to tests to detect the clang/libstdc++ combination.
• Fix for #116, internal macro GHC_NO_DIRENT_D_TYPE allows os detection to support systems without the dirent.d_type member, experimental first QNX compile support as initial use case, fixed issue with filesystems returning DT_UNKNOWN (e.g. reiserfs).
• Pull request #115, added string_view support when clang with libstdc++ is detected.
• Fix for #114, for macOS the pre-Catalina deployment target detection worked only if <Availability.h> was included before <ghc/fs_std.hpp> or <ghc/fs_std_fwd.hpp>/<ghc/fs_std_impl.hpp>.
• Fix for #113, the use of standard chapter numbers was misleading since C++17 and C++20 std::filesystem features are supported, and was replaced by the tag-like chapter names that stay (mostly) consistent over the versions.