Having trouble finding a stronghold to gather these new blocks? Here's a method to get them without having to hunt one down.
For starters, make yourself some Stone Brick steps and press "F3" to bring up your debug menu with coordinates.
There's a handy new variable "F" which determines the direction you are facing.
In order to get Mossy and Cracked Stone blocks, you have to place your stairs and dig them up.
Which block that pops out is determined by the direction you were facing when placing the steps.
F: 2 = Regular (stacks as a separate pile in inventory but has no visual difference to crafted Stone Brick)
Here is an example of placement:
The block next to each stair is what the orientation drops when mined.