Final release for STL-style deque

This final release marks the last time I intend to maintain the STL-style priority_deque. If this is updated later, it will be to add a Boost-style priority_deque.

No known bugs exist, strong (rollback) exception safety is provided in most cases, documentation is complete, and enforcing thread safety has proven impractical at best. I see no further improvements to make.

STL-style Priority Deque and Interval Heap

Implements interval-heap management function templates and an STL-style priority deque class template. Performance an exception-handling have been improved slightly since v1.0.

If your compiler does not support std::thread, threading may be disabled by the following line:
#define BOOST_HEAP_INTERVAL_HEAP_USE_STD_THREAD false

The optional built-in mutex locking has been removed. It would only encourage bad programming habits, while crippling the performance of the deque.