*`ERC1155`: added support for a base implementation, non-standard extensions and a preset contract. ([#2014](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2014), [#2230](https://github.com/OpenZeppelin/openzeppelin-contracts/issues/2230))
### Improvements
*`ReentrancyGuard`: reduced overhead of using the `nonReentrant` modifier. ([#2171](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2171))
*`AccessControl`: added a `RoleAdminChanged` event to `_setAdminRole`. ([#2214](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2214))
* Made all `public` functions in the token preset contracts `virtual`. ([#2257](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2257))
