Added examples 2, 3, 4

2: Calculate the number of 1's in register $t0 and store the result in
$t3

3: Obtain the 16 first bits of a register ($t0) and store them in the
16 last bits of other register ($t1)

4: Determine if the number stored in $t2 is even. If $t2 is even the
program stores 1 in $t1, else stores 0 in $t1