Ensure manage_exception_state uses correct TLS

[zhykzhykzhyk]

Solves #323

[CreoValis]

Wouldn't access through a volatile * be a better solution here? The "no inline" spec probably works around the issue, but that just seems to push the dtor body to the point where gcc couldn't "see into it" to optimize it away.
I think using a volatile pointer cast would forbid it from even optimizing it away.

Like so:

    manage_exception_state() {
        exception_state_ = *(volatile __cxa_eh_globals *)__cxa_get_globals();
    }
    ~manage_exception_state() {
        *(volatile __cxa_eh_globals *)__cxa_get_globals() = exception_state_;
    }
`