binutils/bfd: Require 64-bit integer support for vax

Otherwise, e.g., gas cannot assemble 64-bit immediates correctly on
ILP32 hosts.

Thanks hans@ for analysis:
https://mail-index.netbsd.org/port-vax/2023/11/23/msg004546.html

external/gpl3/binutils/dist/bfd/config.bfd

@@ -1511,6 +1511,13 @@ case "${targ_defvec} ${targ_selvecs}" in
     ;;
 esac
 
+# vax natively supports 64-bit integers.
+case "${targ_defvec} ${targ_selvecs}" in
+  *vax*)
+    want64=true
+    ;;
+esac
+
 case "${host64}${want64}" in
   *true*)
     targ_selvecs="${targ_selvecs} ${targ64_selvecs}"