Codechange: Add parameterless Flip() method to BaseBitSet.

This allows flipping all valid bits.

src/core/base_bitset_type.hpp

@@ -108,6 +108,16 @@ public:
 		return static_cast<Timpl&>(*this);
 	}
 
+	/**
+	 * Flip all bits.
+	 * @returns The bit set
+	 */
+	inline constexpr Timpl &Flip()
+	{
+		this->data ^= Tmask;
+		return static_cast<Timpl&>(*this);
+	}
+
 	/**
 	 * Flip the value-th bit.
 	 * @param value Bit to flip.