Fixes a repeated stop on the first line of a range-over-func body when
stepping through a program. The entry point breakpoint is changed to a
special breakpoint that, when hit:
- clears the current temporary breakpoints
- sets breakpoints like 'next' would, and
- resumes execution.
Move all tests of the functionality of proc.next,
proc.(*TargetGroup).Next, proc.(*TargetGroup).Step,
proc.(*TargetGroup).StepOut to their own test file.
