Squashed 'src/leveldb/' changes from be1b0ff..be91006

936b461 Merge upstream LevelDB 1.13.
748539c LevelDB 1.13

git-subtree-dir: src/leveldb
git-subtree-split: be9100673b05cec1662a54d0b7a59e4317fdda86
Silence useless warning in src/json/json_spirit_writer_template.h to make important warnings easier to see.

warning: typedef ‘Char_type’ locally defined but not used [-Wunused-local-typedefs]
Refactor: pull alert string sanitization into util

Rebased-from: 17faf562629cd27f00fc138e218ebcc1ce071765
special case DoS value == 0 in ProcessMessage()

- prevents unneeded log messages, which could make users think something
  bad was happening

Squashed: style-police code cleanup
Add some additional logging to give extra network insight.
Store and use a sanitized subVer

Rebased-from: a946aa8d3ec7009ac670eeb65a525efe5eeb6e84
Release notes for 0.8.6
Increase default -blockmaxsize/prioritysize to 300K/30K
Remove CENT-output free transaction rule when relaying

Remove the (relay/mempool) rule that all outputs of free transactions
must be greater than 0.01 XBT. Dust spam is now taken care of by making
dusty outputs non-standard.
Lower maximum size for free transaction creation

Changes the maximum size of a free transaction that will be created
from 10,000 bytes to 1,000 bytes.

The idea behind this change is to make the free transaction area
available to a greater number of people; with the default 27K-per-block,
just three very-large very-high-priority transactions could fill the space.