[yul] Implements EVM codegen for break/continue plus respective tests & ChangeLog entry.

test/libsolidity/semanticTests/asmForLoop/for_loop_break.sol

@@ -0,0 +1,13 @@
+contract C {
+    function f() public returns (uint i) {
+        assembly {
+            for {} lt(i, 10) { i := add(i, 1) }
+            {
+                if eq(i, 6) { break }
+                i := add(i, 1)
+            }
+        }
+    }
+}
+// ----
+// f() -> 6

test/libsolidity/semanticTests/asmForLoop/for_loop_continue.sol

@@ -0,0 +1,13 @@
+contract C {
+    function f() public returns (uint k) {
+        assembly {
+            for {let i := 0} lt(i, 10) { i := add(i, 1) }
+            {
+                if eq(mod(i, 2), 0) { continue }
+                k := add(k, 1)
+            }
+        }
+    }
+}
+// ----
+// f() -> 5

test/libsolidity/semanticTests/asmForLoop/for_loop_nested.sol

@@ -0,0 +1,20 @@
+contract C {
+    function f(uint x) public returns (uint i) {
+        assembly {
+            for {} lt(i, 10) { i := add(i, 1) }
+            {
+                if eq(x, 0) { i := 2 break }
+                for {} lt(x, 3) { i := 17 x := 9 } {
+                    if eq(x, 1) { continue }
+                    if eq(x, 2) { break }
+                }
+                if eq(x, 4) { i := 90 }
+            }
+        }
+    }
+}
+// ----
+// f(uint256): 0 -> 2
+// f(uint256): 1 -> 18
+// f(uint256): 2 -> 10
+// f(uint256): 4 -> 91