[SMTChecker] Refactor CHC loops and add if blocks

test/libsolidity/smtCheckerTests/loops/while_nested_break_fail.sol

@@ -0,0 +1,33 @@
+pragma experimental SMTChecker;
+
+contract C
+{
+	function f(uint x, uint y, bool b, bool c) public pure {
+		require(x < 10);
+		while (x < 10) {
+			if (b) {
+				++x;
+				if (x == 10)
+					x = 15;
+			}
+			else {
+				require(y < 10);
+				while (y < 10) {
+					if (c)
+						++y;
+					else {
+						y = 20;
+						break;
+					}
+				}
+				assert(y >= 15);
+				x = 15;
+				break;
+			}
+		}
+		assert(x >= 20);
+	}
+}
+// ----
+// Warning: (329-344): Assertion violation happens here
+// Warning: (380-395): Assertion violation happens here