Made sanity checks include line and file numbers.
Cherry-picked mlucy_3288
Fix GCC compilation in next.
Make r.point deterministic
Merge branch 'v1.15.x' into next

Conflicts:
	src/rdb_protocol/terms/geo.cc
	src/rdb_protocol/terms/type_manip.cc
fixing use of SimpleQueue on python3.4
Fix for `slice_datum_stream_t` logic so that `batchspec_t::all` actually reads everything.  (Also, minor performance tweaks to scaledown logic and some cleanup.)
git cherry-pick 505d7d9 (conflict resolved)
Making range changefeeds work.