Initial merge of some of the iOS 8 / Mac OS X Yosemite specific
lldb support.  I'll be doing more testing & cleanup but I wanted to
get the initial checkin done.

This adds a new SBExpressionOptions::SetLanguage API for selecting a
language of an expression.

I added adds a new SBThread::GetInfoItemByPathString for retriving
information about a thread from that thread's StructuredData.

I added a new StructuredData class for representing
key-value/array/dictionary information (e.g. JSON formatted data).
Helper functions to read JSON and create a StructuredData object,
and to print a StructuredData object in JSON format are included.

A few Cocoa / Cocoa Touch data formatters were updated by Enrico
to track changes in iOS 8 / Yosemite.

Before we query a thread's extended information, the system runtime may
provide hints to the remote debug stub that it will use to retrieve values
out of runtime structures.  I added a new SystemRuntime method
AddThreadExtendedInfoPacketHints which allows the SystemRuntime to add
key-value type data to the initial request that we send to the remote stub.

The thread-format formatter string can now retrieve values out of a thread's
extended info structured data.  The default thread-format string picks up
two of these - thread.info.activity.name and thread.info.trace_messages.

I added a new "jThreadExtendedInfo" packet in debugserver; I will
add documentation to the lldb-gdb-remote.txt doc soon.  It accepts
JSON formatted arguments (most importantly, "thread":threadnum) and
it returns a variety of information regarding the thread to lldb
in JSON format.  This JSON return is scanned into a StructuredData
object that is associated with the thread; UI layers can query the
thread's StructuredData to see if key-values are present, and if
so, show them to the user.  These key-values are likely to be
specific to different targets with some commonality among many
targets.  For instance, many targets will be able to advertise the
pthread_t value for a thread.

I added an initial rough cut of "thread info" command which will print
the information about a thread from the jThreadExtendedInfo result.
I need to do more work to make this format reasonably.

Han Ming added calls into the pmenergy and pmsample libraries if
debugserver is run on Mac OS X Yosemite to get information about the
inferior's power use.

I added support to debugserver for gathering the Genealogy information
about threads, if it exists, and returning it in the jThreadExtendedInfo
JSON result.