Implement C++14 std::make_reverse_iterator
Refactor base_uint<> and STAmount::getText:

base_uint<>:
* Remove unnecessary typedefs and derived classes
* Factor out common code and eliminate redundancies
* Add tag support to improve type safety
* base_uint::ToString() -> to_string(base_uint const&)
* base_uint::GetHex() -> to_string(base_uint const&)

STAmount::getText:
* Don't overallocate
* Eliminate unnecessary copying
Use last closed ledger for old pathfinding
Rework handling of modified ledger nodes:
* Track dirty nodes in a set
* Make flushDirty a member function
* Don't write deleted nodes
* Make sure new nodes are shareable
* Put new nodes in the treeNodeCache
Keep SHAMapNodes that fault in handling client requests.
Refactor RippleCalc.cpp:

* Add comments
* Restrict code to 80 colums
* Remove boost::format
* Remove BOOST_FOREACH
* Make members private
* Add ripple_unordered_set to UnorderedContainers.h
* Replace boost::unordered_set with ripple::unordered_set
Fix vs2013 availability of make_reverse_iterator
SHAMap::canonicalize must return a node with the correct ID
Put newly-created nodes in the treeNodeCache
Dispatch incoming TX set data
At level 64, only leaves are allowed
Fetch pack cleanups:
* Limit backed up fetch pack requests
* Cleanups
* Dispatch fetch packs sooner
Make I/O latency available through server_info
Remove redundant checkAccept call
CBase58Data Refactoring:

* Remove unnecessary functions.
* Load from a base_uint const& - don't use void pointers.
* Free comparison functions.
* Explicitly specify encoding alphabet.
* Miscellaneous cleanups.
Autobridging future support:
* Refactor and cleanup transactors
* Introduce new direct and bridged transactors
* Rename existing transactor to indicate legacy status
* New direct transactor defaults to being turned off (preserve legacy behavior)
Fix lexicographical compare during tfRequireAuth processing
Update .gitattributes
Squashed 'src/snappy/snappy/' content from commit 1ff9be9

git-subtree-dir: src/snappy/snappy
git-subtree-split: 1ff9be9b8fafc8528ca9e055646f5932aa5db9c4
Merge commit '8b0602a5824199d495f6720ef2447f695179257a' as 'src/snappy/snappy'