[backend]将testdata/下的测例替换为了赛方测试用例，更新了测试脚本

testdata/functional/48_assign_complex_expr.sy

@@ -0,0 +1,18 @@
+// Use complex expression in assign structure
+int main () {
+    int a;
+    int b;
+    int c;
+    int d;
+    int result;
+    a = 5;
+    b = 5;
+    c = 1;
+    d = -2;
+    result = (d * 1 / 2)  + (a - b) - -(c + 3) % 2;
+    putint(result);
+    result = ((d % 2 + 67) + -(a - b) - -((c + 2) % 2));
+    result = result + 3;
+    putint(result);
+    return 0;
+}