add iocp crash mock test (to reproduce the issue #985)

[jimying]

use this patch to reproduce crash issue #985 in msys2:

1. modify aconfigure

   #ac_os_objs=ioqueue_select.o
   ac_os_objs=ioqueue_winnt.o
   To set iocp as the default ioqueue framework
   

2. modify pjlib/src/pjlib-test/test.h

   set the macro TEST_DEFAULT=0
   To disable other tests and only enable iocp_crash_test
   

3. build and run with gdb

   # build
   export CFLAGS="-g -O0"
   ./configure ...
   make -C pjlib/build dep
   make -C pjlib/build -j 8
   # run
   cd pjlib/bin
   gdb ./pjlib-test-x86_64-w64-mingw32.exe

Follow the steps, it can 100% reproduce the crash.

PS: This is just a temporary test and is not intended to be submitted into master branch