Define a function combining vm entry lookup and clip-start

[dougm]

Summary

Most uses of vm_map_clip_start follow a call to vm_map_lookup. Define an inline function vm_map_lookup_clip_start that invokes them both and use it in places that invoke both. Drop a couple of local variables made unnecessary by this function.

[pho]

I ran a preliminary 5 hour tests + a buildworld with D22987.66203.diff on r356250. No problems seen.

[dougm]

Add an important omitted line.

[pho]

I ran a full stress2 test on r356314 + D22987.66269.diff. No problems seen.

[dougm]

Resolve conflicts.

[markj]

Seems reasonable to me.

sys/vm/vm_map.c

2418

This line should be indented by four spaces.

3754

This comment is still missing a period. I'm not sure it is very useful to begin with.