Bit operations: Test a bit
	Problem: given int i, is bit n set (equal to 1)?
							bn			b0
		i	0000	0000	0000	0000	0000	0000	0000	0010
							bit n
		How can we test if this bit is 1?
		We can use & operator with a "mask" variable:
		mask	0000	0000	0000	0000	0010	0000	0000	0000
		if (i & mask)
			printf ("yes");
		else
			printf ("no");
	What is the problem with this?
		We would need 32 different masks, depending on the value of n!
	Answer:
		i  & (1 << n)			/* idiom */
	or
		(i >> n) & 1			(Shift nth bit to first location, compare to mask of 1)