Partial fix of t/local/31_rsa_generate_key.t memory leaks

[nataraj-hates-MS-for-stealing-github]

If you build perl and Net::SSLleay with Address Sanitizer and run tests, t/local/31_rsa_generate_key.t will fail with some Memory Leak error messages. There are two parts of this problem.

Second part: You should explicitly free RSA structure created with RSA_generate_key, when it is no longer in use this will prevent unnecessary memory leaks. This patch solves this problem.

First part: Test that checks failure with not-proper callback scalar value

dies_like(sub {
        Net::SSLeay::RSA_generate_key(2048, 0x10001, 1);
}, qr/Undefined subroutine &main::1 called/, 'RSA_generate_key with invalid callback');

also causes memory leak.

As far as I can get this happens because RSA_generate_key from SSLeay.xs allocate something, then calls RSA_generate_key_ex with ssleay_RSA_generate_key_cb_invoke as a callback. And ssleay_RSA_generate_key_cb_invoke calls count = call_sv( cb->func, G_VOID|G_DISCARD ); that throws an exception if cb->func is not a function. Thus we do not free what have been allocated in RSA_generate_key and go straight to dies_like exception catcher.

I guess best solution would be to catch that exception in RSA_generate_key, free the staff, and then rethrow it. Because there can be any exception in a call back, even user generated. But such trick is beyond my power for now.

So this patch will fix only RSA_free related things.

PS You can find instruction on how to build perl in this module using ASan in #469

PPS please refer me as NATARAJ (Nikolay Shaplov) if you ever would like to mention me anywhere...