Enhanse the thread interface to do something quasi inteligent

Enhanse the thread interface to do something quasi inteligent
with the function name passed to be used as a thread name.  Leaving
the trailing _thread is just redundant so just strip it this
make the thread names far more readable.

Use a strncpy in spl-mutex  just to be safe.

git-svn-id: https://outreach.scidac.gov/svn/spl/trunk@107 7e1ea52c-4ff2-0310-8f11-9dd32ca42a1c