Changed PTHREAD_CREATE_JOINABLE to PTHREAD_CREATE_DETACHED
Changed PTHREAD_CREATE_JOINABLE to PTHREAD_CREATE_DETACHED

I did this because it fixes a *possible* (though not actual)
memory leak according to valgrind when using >1 thread. Having the
threads be joinable it more ideal conceptually, but the join
functionality for pthreads doesn't seem to work (probably my own
misunderstanding). This alleged leak is now fixed.

ridgelab/findSSRs,ridgelab/SA-SSR,ridgelab/SA-SSR,ridgelab/findSSRs