ADD: Decrease maxSupply when VADER burnt, increase when minted.

[strictly-scarce]

To prevent emissions eroding into the supply of VADER and causing a deadlock into the future, the maxSupply should be responsive to how much has been burnt (or minted back).

Note: This does prevent an inflation-risk in the protocol if there is a successful attack on the anchorPrice that allows someone to mint, depress price, burn, repeatedly.

Slip-based fees should slow this down, but the DAO can also respond by increasing usdv.blockDelay() to slow down the attack cycle.