Fix PR 17206

As reported in PR 17206, an internal error is triggered when command
until is executed.  In infcmd.c:until_next_command, step_range_end is
set to 'pc',

  if (!func)
    {
      struct bound_minimal_symbol msymbol = lookup_minimal_symbol_by_pc (pc);

      if (msymbol.minsym == NULL)
	error (_("Execution is not within a known function."));

      tp->control.step_range_start = BMSYMBOL_VALUE_ADDRESS (msymbol);
      tp->control.step_range_end = pc;
    }

and later in infrun.c:resume, the assert below is triggered in PR
17206.

  if (tp->control.may_range_step)
    {
      /* If we're resuming a thread with the PC out of the step
	 range, then we're doing some nested/finer run control
	 operation, like stepping the thread out of the dynamic
	 linker or the displaced stepping scratch pad.  We
	 shouldn't have allowed a range step then.  */
      gdb_assert (pc_in_thread_step_range (pc, tp));
    }

In until_next_command, we set step range to [XXX, pc), so pc isn't
within the range.  pc_in_thread_step_range returns false and the
assert is triggered.  AFAICS, the range we want in until_next_command
is [XXX, pc] instead of [XXX, pc), because we want to program step
until greater than pc.  This patch is to set step_range_end to
'pc + 1'.  Running until-nodebug.exp with unpatched GDB will get the
following fail,

FAIL: gdb.base/until-nodebug.exp: until 2 (GDB internal error)

and the fail goes away when the fix is applied.

gdb:

2014-07-29  Yao Qi  <yao@codesourcery.com>

	PR gdb/17206
	* infcmd.c (until_next_command): Set step_range_end to PC + 1.

gdb/testsuite:

2014-07-29  Yao Qi  <yao@codesourcery.com>

	PR gdb/17206
	* gdb.base/until-nodebug.exp: New.