Change the type of ret in fqpeek() and fqpop() to be volatile
Change the type of ret in fqpeek() and fqpop() to be volatile

This will suppress a warning from GCC about possible clobbering by
setjmp() and longjmp(). This procedures are used by
pthread_cleanup_push(). This warning is correct but irrelevant because
the value of ret cannot be used after setjmp() returns the second time
because the cleanup process will terminate execution.

byannoni/qthreads