Consistent vm_map_entry loop naming

[dougm]

Summary

Where 'current' is used to index over vm_map entries, use 'entry'. Where 'entry' is used to identify the starting point for iteration, use 'first_entry'. These are the naming conventions used in most of the vm_map.c code. Where VM_MAP_ENTRY_FOREACH can be used, do so. Squeeze a few lines to fit in 80 columns.

[alc]

sys/vm/vm_map.c

2521–2523

Eliminate extra parens around entry->protection.

2699–2700

I think that it's reasonable for this patch to wrap these lines.

3387

!= 0