Add "available since" comments in documentation

contracts/drafts/EIP712.sol

@@ -18,6 +18,8 @@ pragma solidity >=0.6.0 <0.8.0;
  *
  * NOTE: This contract implements the version of the encoding known as "v4", as implemented by the JSON RPC method
  * https://docs.metamask.io/guide/signing-data.html[`eth_signTypedDataV4` in MetaMask].
+ *
+ * _Available since v3.4._
  */
 abstract contract EIP712 {
     /* solhint-disable var-name-mixedcase */

contracts/drafts/ERC20Permit.sol

@@ -15,6 +15,8 @@ import "./EIP712.sol";
  * Adds the {permit} method, which can be used to change an account's ERC20 allowance (see {IERC20-allowance}) by
  * presenting a message signed by the account. By not relying on `{IERC20-approve}`, the token holder account doesn't
  * need to send a transaction, and thus is not required to hold Ether at all.
+ *
+ * _Available since v3.4._
  */
 abstract contract ERC20Permit is ERC20, IERC20Permit, EIP712 {
     using Counters for Counters.Counter;

contracts/introspection/ERC165Checker.sol

@@ -47,6 +47,8 @@ library ERC165Checker {
      * is that some interfaces may not be supported.
      *
      * See {IERC165-supportsInterface}.
+     *
+     * _Available since v3.4._
      */
     function getSupportedInterfaces(address account, bytes4[] memory interfaceIds) internal view returns (bool[] memory) {
         // an array of booleans corresponding to interfaceIds and whether they're supported or not

contracts/math/SafeMath.sol

@@ -18,6 +18,8 @@ pragma solidity >=0.6.0 <0.8.0;
 library SafeMath {
     /**
      * @dev Returns the addition of two unsigned integers, with an overflow flag.
+     *
+     * _Available since v3.4._
      */
     function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
         uint256 c = a + b;
@@ -27,6 +29,8 @@ library SafeMath {
 
     /**
      * @dev Returns the substraction of two unsigned integers, with an overflow flag.
+     *
+     * _Available since v3.4._
      */
     function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
         if (b > a) return (false, 0);
@@ -35,6 +39,8 @@ library SafeMath {
 
     /**
      * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
+     *
+     * _Available since v3.4._
      */
     function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {
         // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
@@ -48,6 +54,8 @@ library SafeMath {
 
     /**
      * @dev Returns the division of two unsigned integers, with a division by zero flag.
+     *
+     * _Available since v3.4._
      */
     function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
         if (b == 0) return (false, 0);
@@ -56,6 +64,8 @@ library SafeMath {
 
     /**
      * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
+     *
+     * _Available since v3.4._
      */
     function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
         if (b == 0) return (false, 0);

contracts/presets/ERC20PresetFixedSupply.sol

@@ -12,6 +12,8 @@ import "../token/ERC20/ERC20Burnable.sol";
  *
  * This contract uses {ERC20Burnable} to include burn capabilities - head to
  * its documentation for details.
+ *
+ * _Available since v3.4._
  */
 contract ERC20PresetFixedSupply is ERC20Burnable {
     /**

contracts/presets/ERC777PresetFixedSupply.sol

@@ -8,6 +8,8 @@ import "../token/ERC777/ERC777.sol";
  *
  *  - Preminted initial supply
  *  - No access control mechanism (for minting/pausing) and hence no governance
+ *
+ * _Available since v3.4._
  */
 contract ERC777PresetFixedSupply is ERC777 {
     /**

contracts/proxy/BeaconProxy.sol

@@ -11,6 +11,8 @@ import "./IBeacon.sol";
  *
  * The beacon address is stored in storage slot `uint256(keccak256('eip1967.proxy.beacon')) - 1`, so that it doesn't
  * conflict with the storage layout of the implementation behind the proxy.
+ *
+ * _Available since v3.4._
  */
 contract BeaconProxy is Proxy {
     /**

contracts/proxy/Clones.sol

@@ -12,6 +12,8 @@ pragma solidity >=0.6.0 <0.8.0;
  * The library includes functions to deploy a proxy using either `create` (traditional deployment) or `create2`
  * (salted deterministic deployment). It also includes functions to predict the addresses of clones deployed using the
  * deterministic method.
+ *
+ * _Available since v3.4._
  */
 library Clones {
     /**

contracts/utils/Address.sol

@@ -148,7 +148,7 @@ library Address {
      * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
      * but performing a delegate call.
      *
-     * _Available since v3.3._
+     * _Available since v3.4._
      */
     function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
         return functionDelegateCall(target, data, "Address: low-level delegate call failed");
@@ -158,7 +158,7 @@ library Address {
      * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
      * but performing a delegate call.
      *
-     * _Available since v3.3._
+     * _Available since v3.4._
      */
     function functionDelegateCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
         require(isContract(target), "Address: delegate call to non-contract");

contracts/utils/EnumerableMap.sol

@@ -235,6 +235,8 @@ library EnumerableMap {
     /**
      * @dev Tries to returns the value associated with `key`.  O(1).
      * Does not revert if `key` is not in the map.
+     *
+     * _Available since v3.4._
      */
     function tryGet(UintToAddressMap storage map, uint256 key) internal view returns (bool, address) {
         (bool success, bytes32 value) = _tryGet(map._inner, bytes32(key));