Change CHC encoding to functions forest instead of explicit CFG

test/libsolidity/smtCheckerTests/functions/library_constant.sol

@@ -0,0 +1,26 @@
+pragma experimental SMTChecker;
+
+library l1 {
+
+	uint private constant TON = 1000;
+	function f1() public pure {
+		assert(TON == 1000);
+		assert(TON == 2000);
+	}
+	function f2(uint x, uint y) internal pure returns (uint) {
+		return x + y;
+	}
+}
+
+contract C {
+	function f(uint x) public pure {
+		uint z = l1.f2(x, 1);
+		assert(z == x + 1);
+	}
+}
+// ----
+// Warning: (136-155): Assertion violation happens here
+// Warning: (229-234): Overflow (resulting value larger than 2**256 - 1) happens here
+// Warning: (300-302): Assertion checker does not yet implement type type(library l1)
+// Warning: (229-234): Overflow (resulting value larger than 2**256 - 1) happens here
+// Warning: (327-332): Overflow (resulting value larger than 2**256 - 1) happens here

test/libsolidity/smtCheckerTests/functions/library_constant_2.sol

@@ -0,0 +1,9 @@
+pragma experimental SMTChecker;
+
+library l1 {
+
+	uint private constant TON = 1000;
+	function f1() public pure {
+		assert(TON == 1000);
+	}
+}