Fix bugs, add propper tests

old_tests/parser/expressions.mcl

@@ -0,0 +1,8 @@
+let a = 1 * 3 == 4;
+let b = 3/4 == *a;
+let c = (a->b.c->d) / 2;
+let d = 2 / a->b.c->d;
+let e = a->b.c->d / 2;
+let f = a.b.c.d / 2;
+let g = a.b[*a.c] * 5;
+