Use of non-portable C header declarations

[YexuanXiao]

Lines 107-108 use size_t and ptrdiff_t without the std:: prefix. According to the C++ standard, these typedefs aren't available in the global namespace.

cstring_view/include/beman/cstring_view/cstring_view.hpp

Lines 107 to 108 in 097c505

	using size_type = size_t;
	using difference_type = ptrdiff_t;