Running the current tree against my software-single-step-on-x86_64

Running the current tree against my software-single-step-on-x86_64
branch showed some extra assertions I have in place triggering.  Turns
out my previous change to 'resume' was incomplete, and we mishandle
the 'hw_step' / 'step' variable pair.  (I swear I had fixed this, but
I guess I lost that in some local branch...)

Tested on x86_64 Fedora 20.

gdb/
2014-05-29  Pedro Alves  <palves@redhat.com>

	* infrun.c (resume): Rename local 'hw_step' to 'entry_step'
	and make it const.  When a single-step decays to a continue,
	clear 'step', not 'hw_step'.  Pass whether the caller wanted
	to step to user_visible_resume_ptid, not what we ask the
	target to do.