tccgen.c: Try to make sizeof(!x) work.

tests/tests2/27_sizeof.*: Add test.

tests/tests2/27_sizeof.c

@@ -10,6 +10,8 @@ int main()
    printf("%d\n", sizeof(b));
    printf("%d\n", sizeof(c));
 
+   printf("%d\n", sizeof(!a));
+
    return 0;
 }
 

tests/tests2/27_sizeof.expect

@@ -1,3 +1,4 @@
 1
 4
 8
+4