Disable thread naming on Win64 for now.

We can't use _try/_except without the C runtime, and we can't use inline
 asm with the Win64 compiler. We'll need to move this to an .asm file or
 something later.

--HG--
extra : rebase_source : 2f1b255b44b4a5d9b88d9257eb3e064e485dd760
Workaround for compiling with /W4 warnings on Visual C++.