Add small tests for unsafe_bool and unsafe_int casting

Author: rkalis

packages/cashc/test/compiler/CastTypeError/unsafe_bool_cast_bytes4.cash

@@ -0,0 +1,5 @@
+contract Test(bytes4 x) {
+    function test() {
+        require(unsafe_bool(x));
+    }
+}

packages/cashc/test/compiler/CastTypeError/unsafe_int_cast_sig.cash

@@ -0,0 +1,5 @@
+contract Test(sig x) {
+    function test(bytes4 y) {
+        require(unsafe_int(x) > unsafe_int(y));
+    }
+}

packages/cashc/test/valid-contract-files/unsafe_bool_cast.cash

@@ -0,0 +1,5 @@
+contract Test(int x) {
+    function test() {
+        require(unsafe_bool(x));
+    }
+}

packages/cashc/test/valid-contract-files/unsafe_int_cast.cash

@@ -0,0 +1,5 @@
+contract Test(bytes4 x) {
+    function test(bytes4 y) {
+        require(unsafe_int(x) > unsafe_int(y));
+    }
+}