Fixed core dump in GetFunctorStartAddress() for ARM platforms.

The method to determine, if a pointer to a member function points to a virtual method or not, depends on the ABI. Please see also:
* http://infocenter.arm.com/help/topic/com.arm.doc.ihi0041e/IHI0041E_cppabi.pdf chapter 3.2
* https://blog.mozilla.org/nfroyd/2014/02/20/finding-addresses-of-virtual-functions/

c++/src/kj/async-inl.h

@@ -285,9 +285,14 @@ class PtmfHelper {
 #undef BODY
 
   void* apply(void* obj) {
+#if defined(__arm__) || defined(__mips__) || defined(__aarch64__)
+    if (adj & 1) {
+      ptrdiff_t voff = (ptrdiff_t)ptr;
+#else
     ptrdiff_t voff = (ptrdiff_t)ptr;
     if (voff & 1) {
       voff &= ~1;
+#endif
       return *(void**)(*(char**)obj + voff);
     } else {
       return ptr;