1.4.0

This release of string_view lite contains the following fixes and changes:

Fixes:

• Fix operator==() on wstring_view and wchar_t raw string (#30, thanks to @gongminmin).

Changes:

• Add option -Wshadow for gcc, clang.
• Avoid shadowing (#31, thanks @mattyclarkson).
• Add string_view comparison with std::string and const char * for older compilers.
• Non-recursive variant of detail::length() for compilers with maximum recursion depth in compile-time constexpr evaluation (#29, thanks @AdmiralCurtiss).
• Improve MSVC version table, nonstd-lite-project issue 38.
• Point conan badge to conan-center (thanks @flexferrum).
• Use #include in code on godbolt, nonstd-lite-project issue 36.