
This patch allows a user to customize the stack size of the threads used by pupnp through the new THREAD_STACK_SIZE variable. This is especially useful on embedded systems with limited memory where the user can set THREAD_STACK_SIZE to ITHREAD_STACK_MIN. However, as this modification can have side effects, I set 0 as the default value, so threads will continue to use the default stack size of the system (which varies greatly as stated in https://computing.llnl.gov/tutorials/pthreads/). (cherry picked from commit 467f9987a135986419222da968562aab26a3e637)