Merge pull request #9230 from ethereum/issue-8716

Add unit denomination ``gwei``

test/libsolidity/syntaxTests/denominations/denominations.sol

@@ -2,5 +2,6 @@ contract C {
 	uint constant a = 1 wei + 2 szabo + 3 finney + 4 ether;
 	uint constant b = 1 seconds + 2 minutes + 3 hours + 4 days + 5 weeks;
 	uint constant c = 2 szabo / 1 seconds + 3 finney * 3 hours;
+	uint constant d = 2 gwei / 1 seconds + 3 finney * 3 hours;
 }
 // ----

test/libsolidity/syntaxTests/denominations/gwei.sol

@@ -0,0 +1,3 @@
+contract C {
+	uint constant gwei = 1 gwei;
+}

test/libsolidity/syntaxTests/parsing/literal_constants_with_ether_subdenominations.sol

@@ -1,15 +1,16 @@
-contract c {
+contract C {
     function f() public
     {
          a = 1 wei;
          b = 2 szabo;
          c = 3 finney;
-         b = 4 ether;
+         d = 4 ether;
+         e = 5 gwei;
     }
     uint256 a;
     uint256 b;
     uint256 c;
     uint256 d;
+    uint256 e;
 }
 // ----
-// Warning 2519: (170-179): This declaration shadows an existing declaration.