Bug 1935

The following features for sequences would be desirable, and I know how to
implement them, so I am including them in the sequence meta-bug:

1) Sequences should have unit tests for:
   a) Basic functionality.
   b) Exception safety with respect to memory allocations
   c) Exception safety with respect to copy-constructors in the underlying type.
   d) Number of allocations in constructors and modifiers.

2) Sequences should be configurable, on at least the underlying type with
respect to:
   a) Index checking in operator[]
   b) What actions are performed when operation[] is used incorrectly.
   c) Incorrect assignment to sequences with release=FALSE.
   d) Allocators used for allocbuf() and freebuf().

3) The code for sequences is reimplemented around 8 times in TAO.  We need to
refactor without mercy!