All pool threads are named "pool" and this a bit annoying when looking
at system-wide traces or statistics for a system where several
applications use thread pools.  Include the prgname in the thread names
to get a better default name.  The total length including the "pool-"
prefix is limited to 16 bytes in order for it to work on all systems.

Change-Id: I473a9f534c4630f3e81da72ff96d8f593c60efac