Fix regression from multi-arch patch.

This fixes the regression reported at
<http://sourceware.org/ml/gdb-patches/2013-06/msg00185.html>.

GDBserver was reaching:

static int
regsets_fetch_inferior_registers (struct regsets_info *regsets_info,
				  struct regcache *regcache)
{
  struct regset_info *regset;
  int saw_general_regs = 0;
  int pid;
  struct iovec iov;

  regset = regsets_info->regsets;

  pid = lwpid_of (get_thread_lwp (current_inferior));
  while (regset->size >= 0)
    {
      void *buf, *data;
      int nt_type, res;

      if (regset->size == 0
	  || regsets_info->disabled_regsets[regset - regsets_info->regsets])
	{
>>>>>>>	  regset ++;      <<<<<<<  HERE
	  continue;
	}

Because info->disabled_regsets[] was not being initialized, and that
causes all sorts of wrong.

gdb/gdbserver/
2013-06-11  Pedro Alves  <palves@redhat.com>

	* linux-low.c (initialize_regsets_info): Use xcalloc instead of
	xmalloc.