RFR: 8230877: Rename THREAD_LOCAL_DECL to thread_local

[Kim Barrett]

> On Sep 11, 2019, at 5:37 PM, Kim Barrett <kim.barrett at oracle.com> wrote:
> Instead for VS we probably need to do an MSVC version check to decide
> whether to define thread_local to __declspec(thread), but I don't know which
> version of VS starts providing it natively.  Either that or prune the set of
> (at least purportedly) supported versions somewhat.

According to boost.config and various other places I found, it appears
thread_local first shows up in Visual Studio 2015. So having a
__declspec(thread) definition protected with "#if _MSC_VER < 1900" should do
the trick.