windows: first shot at naming threads with SetThreadDescription().

This is a bleeding edge API, added to Windows 10 Anniversary Edition (build
1607, specifically).

https://msdn.microsoft.com/en-us/library/windows/desktop/mt774976(v=vs.85).aspx

Nothing supports this yet, including WinDbg, Visual Studio, minidumps, etc,
so we still need to also use the RaiseException hack. But presumably tools
will use this API as a more robust and universal way to get thread names
sooner or later, so we'll start broadcasting to it now.

src/thread/windows/SDL_systhread.c

@@ -164,10 +164,36 @@ typedef struct tagTHREADNAME_INFO
 } THREADNAME_INFO;
 #pragma pack(pop)
 
+
+typedef HRESULT (WINAPI *pfnSetThreadDescription)(HANDLE, PCWSTR);
+
 void
 SDL_SYS_SetupThread(const char *name)
 {
-    if ((name != NULL) && IsDebuggerPresent()) {
+    if (name != NULL) {
+        static HMODULE kernel32 = 0;
+        static pfnSetThreadDescription pSetThreadDescription = NULL;
+
+        if (!kernel32) {
+            kernel32 = LoadLibrary(L"kernel32.dll");
+            if (kernel32) {
+                pSetThreadDescription = (pfnSetThreadDescription) GetProcAddress(kernel32, "SetThreadDescription");
+            }
+        }
+
+        if (pSetThreadDescription != NULL) {
+            WCHAR *strw = WIN_UTF8ToString(name);
+            if (strw) {
+                pSetThreadDescription(GetCurrentThread(), strw);
+                SDL_free(strw);
+            }
+        }
+
+        /* Presumably some version of Visual Studio will understand SetThreadDescription(),
+           but we still need to deal with older OSes and debuggers. Set it with the arcane
+           exception magic, too. */
+
+        if (IsDebuggerPresent()) {
             THREADNAME_INFO inf;
 
             /* C# and friends will try to catch this Exception, let's avoid it. */
@@ -186,6 +212,7 @@ SDL_SYS_SetupThread(const char *name)
             RaiseException(0x406D1388, 0, sizeof(inf) / sizeof(ULONG), (const ULONG_PTR*) &inf);
         }
     }
+}
 
 SDL_threadID
 SDL_ThreadID(void)