Implemented assert keyword

tests/programs/assert.q

@@ -0,0 +1,6 @@
+main() {
+	assert 1 != 0
+	assert 1 == 0 || 1 != 0
+	assert 1 != 0 && 2 != 0
+	assert 1 == 0
+}

tests/programs_test.go

@@ -40,6 +40,7 @@ var programs = []struct {
 	{"jump-near", "", "", 0},
 	{"loop", "", "", 0},
 	{"loop-lifetime", "", "", 0},
+	{"assert", "", "", 1},
 }
 
 func TestPrograms(t *testing.T) {