Packport FreeBSD defines from Platform.h in qtdeclarative

This should get QtScript to compile on some more versions of
FreeBSD, including DragonFly.

Task-number: QTBUG-35880
Change-Id: Ie40cf8d1cc8a676d51694e609ddc9f85d22b9b81
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@digia.com>

src/3rdparty/javascriptcore/JavaScriptCore/wtf/Platform.h

@@ -441,7 +441,7 @@
 #endif
 
 /* OS(FREEBSD) - FreeBSD */
-#ifdef __FreeBSD__
+#if defined(__FreeBSD__) || defined(__DragonFly__) || defined(__FreeBSD_kernel__)
 #define WTF_OS_FREEBSD 1
 #endif