std::string_view + other non null-terminated input support for insertion

[Xeverous]

Right now there is such thing in the implementation:

	// Convert char* to string to trigger op<<(..., const std::string )
	template<std::size_t N> inline database_binder& operator <<(database_binder& db, const char(&STR)[N]) { return db << std::string(STR); }
	template<std::size_t N> inline database_binder& operator <<(database_binder& db, const char16_t(&STR)[N]) { return db << std::u16string(STR); }

	 inline database_binder& operator <<(database_binder& db, const std::string& txt) {
		int hresult;
		if((hresult = sqlite3_bind_text(db._stmt.get(), db._next_index(), txt.data(), -1, SQLITE_TRANSIENT)) != SQLITE_OK) {
			errors::throw_sqlite_error(hresult, db.sql());
		}

		return db;
	}

The implementation builds temporary strings (unneded allocation) and loses the information on their length by passing -1.

This looks like a simple thing to fix - while also giving the opportunity to add support for non-null-terminated strings such as std::string_view. I propose database_binder::bind_next(T* ptr, int length).