Bug 20198: quick_exit should not call destructors.

In C++11 18.5.12 says "Objects shall not be destroyed as a
result of calling quick_exit." In C11 quick_exit is silent
about thread object destruction. Therefore to make glibc
C++ compliant we do not call any thread local destructors.
A new regression test verifies the fix.

I will note that C++11 18.5.3 makes it clear that C++
defines additional requirements for _Exit() to prevent it
from executing destructors.

Given that the point of _Exit() is to terminate the process
immediately it makes sense the C and C++ should line up
and avoid calling destructors.

No failures. New regtest passes.