Add miscellaneous missing WinAPI functions, constants, and structures for comctl32, user32, and ux_theme.

core/sys/windows/ux_theme.odin

@@ -9,4 +9,5 @@ PMARGINS :: ^MARGINS
 @(default_calling_convention="system")
 foreign uxtheme {
     IsThemeActive :: proc() -> BOOL ---
+    SetWindowTheme :: proc(hWnd: HWND, pszSubAppName, pszSubIdList: LPCWSTR) -> HRESULT ---
 }