Log Message:
Update to 1.1.0

Changelog:
* packed_trie_map (new)

  * new data structure that implements a trie also known as a prefix
    tree.  This implementation requires all key values be known at
    construction time, after which its content is considered
    immutable.  Internally it packs all its nodes in a single
    contiguous array for space and lookup efficiencies.

* trie_map (new)

  * new data structure that implements a trie.  It works similar to
    packed_trie_map except that this version is mutable.

* multi_type_matrix

  * added a variant of walk() that takes the upper-left and
    lower-right corners to allow walking through a subset of the
    original matrix.

* multi_type_vector

  * fixed incorrect return values of the increment and decrement
    operators of in-block iterators.  They would previously return a
    value_type pointer which did not conform to the behaviors of STL
    iterators.

  * added support for custom event handlers for element block
    acquisitions and releases.

* flat_segment_tree

  * fixed incorrect return values of the increment and decrement
    operators of its leaf-node iterators as in multi_type_vector's
    fix.

* sorted_string_map

  * significantly improved the performance of its find() method by
    switching from using linear search to using binary search.  The
    improvement is especially visible with a large number of elements.