Fix compiler error on VS2013
Add method to give thread low priority

Sometimes when creating a background thread it's useful to tell the
system that it should run with a lower scheduling priority. However,
creating a more flexible method which would take in a priority level
is a bad idea, because there's no use in setting a thread to the
default priority and scheduling to increased priority is usually a bad
idea.

Therefore this commit takes the simple approach and simply offers to
decrease the priority, which should usually work.
Support setting human-readable thread name
Fix some spelling errors in header file
Remove stray semicolon

GCC warns about this in -pedantic mode
Define ATOMIC_FLAG_INIT lazily

On some platforms, bits/atomic_base.h defines this symbol, so we
should pad our definition with an #ifndef to avoid compiler nags about
symbol redefinitions.
Merge pull request #1 from teragonaudio/teragon

Merge all open Teragon fixes