Hi,
Recent gdb code refactor changes LONGEST from a macro to a typedef,
thus the use of it in aarch64-linux-nat.c is no longer valid.

This patch fixes the build failure which is obvious.  Is it OK?

Thanks,
bin

2014-08-21  Bin Cheng  <bin.cheng@arm.com>

* aarch64-linux-nat.c (dr_changed_t): Change the type from
unsigned LONGEST to ULONGEST.