SERVER-9538 Only update BufBuilder's len if successfully grew

Otherwise BSONObj destructor will try to grow again to add EOO byte,
causing a double exception and terminate() call.
Include What You Use for bufreader.h
SERVER-7172 Build support for creating a path in a mutable document.
SERVER-7172 Support testing whether a field is updatable.
SERVER-7172 Remove unused code in test fixtures.
SERVER-7172 Fix dassert to compile
SERVER-7172 Visual Studio -- add new files
SERVER-7172 Field checker now checks for empty fields as well.
SERVER-7172 Allow init() to be called more than once in field parsing (for reuse).
SERVER-7174 Renamed the mods common interface and its calls to be simpler.
SERVER-7174 $set update mod built over the new mods framework.
SERVER-6400: MatchExpression version of Matcher code complete.