gruel thread simplification:
Removed get_new_timeout from thread.h (usrp2_vrt carryover) Basically it was created because of a misunderstanding of the time types; and its only ever called once. This also removes thread.cc
Call posix_time::milliseconds in usrp2 control.cc. Notice that it passes a time_duration rather than a ptime (aka system time).
Added #include <deque> to gr_buffer.h. It turns out that boost posix_time.hpp implicitly included the deque header which was missing from gr_buffer.h
Replaced the include for thread.hpp with only the includes for the boost thread types mentioned in gruel/thread.h. Also, making use of the scoped_lock typedef that comes with boost thread locks. boost 3.5 safe.