Enabling Boost.Thread to be used in the Windows Runtime.
This involves basically 3 changes:
1. Using __declspec(thread) instead of the Tls APIs.
2. Using Windows::System::Threading since Win32 Threading APIs aren't allowed.
3. Updating or replacing some banned APIs like WaitForSingleObject with WaitForSingleObjectEx.
Incorporating feedback: removed copyright, removed some ifdefs.
Merge branch 'develop' of https://github.com/boostorg/thread into feedback
Addressing more feedback:
Reverting disabling thread attributes for WinRT.
Created common GetSystemInfo/GetNativeSystemInfo function.
Fix this_thread get_id() bug on WinRT.
Enabled initializing the Windows Runtime in each test for execution. This
is not when using in Windows store/phone applications, just if a desktop
app.
Fixing up copyrights that got reordered.
Qualifying some functions calls in thread_primitives.hpp to avoid potentially ambiguity.
Removing QueueUserAPC on Windows Runtime.
Merge branch 'develop' into winrt2

Conflicts:
	include/boost/thread/win32/thread_primitives.hpp
	src/win32/gettickcount64.cpp
Merge branch 'winrt2' of https://github.com/MSOpenTech/thread into MSOpenTech-winrt2
Fixed up WinRT support patch not compiling on WinRT.
Merge branch 'MSOpenTech-winrt2' into develop