throw in destructors

[dirk-zimoch]

The destructors ~casAsyncReadIO, ~casAsyncWriteIO, ~casAsyncPVExistIO and ~casAsyncPVAttachIO throw exceptions. This is no longer allowed from C++11 on and the compilers issue warnings:

gcc:

../../../../src/pcas/generic/casAsyncPVExistIO.cc: In destructor ‘virtual casAsyncPVExistIO::~casAsyncPVExistIO()’:
../../../../src/pcas/generic/casAsyncPVExistIO.cc:35:9: warning: ‘throw’ will always call ‘terminate’ [-Wterminate]
   35 |         throw std::logic_error (
      |         ^~~~~~~~~~~~~~~~~~~~~~~~
   36 |             "the server library *must* initiate asynchronous IO destroy" );
      |             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../../../../src/pcas/generic/casAsyncPVExistIO.cc:35:9: note: in C++11 destructors default to ‘noexcept’

clang:

../../../../src/pcas/generic/casAsyncPVExistIO.cc:35:9: warning: '~casAsyncPVExistIO' has a non-throwing exception specification but can still throw [-Wexceptions]
   35 |         throw std::logic_error (
      |         ^
../../../../src/pcas/generic/casAsyncPVExistIO.cc:32:20: note: destructor has a implicit non-throwing exception specification
   32 | casAsyncPVExistIO::~casAsyncPVExistIO ()
      |                    ^

Windows cl:

src\pcas\generic\casAsyncPVExistIO.cc(35): warning C4297: 'casAsyncPVExistIO::~casAsyncPVExistIO': function assumed not to throw an exception but does
src\pcas\generic\casAsyncPVExistIO.cc(35): note: destructor or deallocator has a (possibly implicit) non-throwing exception specification

Not sure how best address this. Ignoring it? Simply adding noexcept(false) "everywhere"? Rewriting the destructors not to throw? But how?