Need to generate special test cases

[wwylele]

test_generator only generates test cases randomly. However, it should also generate test cases regarding to special values, such as 0, 1, -1, 0x7FFFFFFF etc to make sure all the flags work in edge cases. These edge cases has only been tested by hand and I might have missed many more cases.

The biggest problem is that the total amount of test cases would scale up very fast. A full package from current generator, which only contains a small amount of randomized cases for each opcode, would run for more than an hour on 3DS. Adding special test case matrix might increase the run time to a day or something.