Decide whether we may have removed breakpoints based on step_over_info

Decide whether we may have removed breakpoints based on step_over_info

... instead of trap_expected.

Gets rid of one singlestep_breakpoints_inserted_p reference, and is
generally more to the point.

gdb/
2014-10-15  Pedro Alves  <palves@redhat.com>

	* infrun.c (step_over_info_valid_p): New function.
	(resume): Use step_over_info_valid_p instead of checking the
	threads's trap_expected flag.