Pre-release v1.3.2 is not running on Mac OS X

[HerbertKoelman]

iMac-de-herbert:tests herbert$ ./without-cpp11-pthread-tests 5
lib version: cpp-pthread v1.3.1 - bc377cb2421f92243f452c150d5171270020a182 - compiled on Darwin Darwin Kernel Version 15.5.0: Tue Apr 19 18:36:36 PDT 2016; root:xnu-3248.50.21~8/RELEASE_X86_64.
add new work to thread group
add new work to thread group
add new work to thread group
add new work to thread group
add new work to thread group
Segmentation fault: 11

[HerbertKoelman]

Failed to set stacksize, hence in thread_group::start() the thread::thread constructor fails, thowing a thread_exception. When jumping to the catch section the thread_group is freed and the destructor wrongly called a join method on a no_a_thread instance.

[HerbertKoelman]

Better error condition handling.