Implement GShare for the simulator.

**Description**

Implement a Gshare predictor for you in order pipeline processor.

You will implement a branch predictor that uses:

1) 16-entry Branch History Table (BHT) that is initialized to all zeros

with 4 bits of history.

2) Xor, which takes the output of the BHT and the last 4 bits of your PC.

3) This will index into a 16-entry pattern history table

containing a 2-bit state machine. The initial state will be weakly NOT-TAKEN.