#262 tempo2 system call performance

[Stefan Oslowski]

In some situations, it would be highly desirable if tempo2 would use a unique directory rather than locking /tmp/tempo2/$USER. An example of such a situation would be a multi-threaded hierarchical psradd when creating a high S/N standard. In such a situation multiple instances of psradd are running on a small part of data. The call to psradd takes a similar amount of time as the call to tempo2 - this creates a lock between all the instances of psradd.