Move crypto/threads to demo/threads

Reviewed-by: Richard Levitte <levitte@openssl.org>

demos/threads/pthread.sh

@@ -0,0 +1,6 @@
+#!/bin/sh
+#
+# build using pthreads where it's already built into the system
+#
+/bin/rm -f mttest
+gcc -DPTHREADS -I../../include -g mttest.c -o mttest -L../.. -lssl -lcrypto -lpthread -ldl