defmethod on a referred multifn resolves to its home ns

A (defmethod m …) where m is :refer'd from another ns passed the bare symbol to
defmethod-setup, which resolved it in the current ns and created a shadow multifn
— the method never reached the real one. Resolve an unqualified name through the
refer table (then current ns) so it lands on the referred multifn.

The AOT build strips the ns form, so the refer table is empty in a binary; emit
chez-register-refer!/-refer-all! per app ns alongside the existing alias
registrations. build-app's fixture gains a defmethod on a referred multifn.

host/chez/build-smoke.sh

@@ -46,7 +46,8 @@ HELLO FROM A BUILT BINARY!
 args: [alpha bb ccc]
 sum: 10
 greet-default: greet:default
-greet-loud: greet:loud'
+greet-loud: greet:loud
+greet-soft: greet:soft'
 if [ "$got" != "$want" ]; then
   echo "  FAIL: binary output mismatch"
   echo "--- want ---"; echo "$want"