provide portable HOST_LONG_BITS test

Do not hardcode the list of 64-bit CPUs.  Use sizeof(void *) to
compute it.  Renaming it to HOST_LONG_BITS to HOST_POINTER_BITS
is left for later.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>

configure

@@ -1084,13 +1084,15 @@ esac
 
 fi
 
-# host long bits test
-hostlongbits="32"
-case "$cpu" in
-  x86_64|alpha|ia64|sparc64|ppc64|s390x)
-    hostlongbits=64
-  ;;
-esac
+# host long bits test, actually a pointer size test
+cat > $TMPC << EOF
+int sizeof_pointer_is_8[sizeof(void *) == 8 ? 1 : -1];
+EOF
+if compile_object; then
+hostlongbits=64
+else
+hostlongbits=32
+fi
 
 
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