This switches Isolate::ComputeLocation to use baseline code when
computing message locations. This unifies locations between optimized
and non-optimized code by always going through the FrameSummary for
location computation.

R=bmeurer@chromium.org
TEST=message/regress/regress-4266
BUG=v8:4266
LOG=n

Review URL: https://codereview.chromium.org/1331603002

Cr-Commit-Position: refs/heads/master@{#30635}

This makes the compilers agree on the source position of a message
generated by "throw new Error()", it points to the beginning of the
throw directive.

R=titzer@chromium.org
TEST=message/regress/regress-3995
BUG=v8:3995
LOG=N

Review URL: https://codereview.chromium.org/1049703002

Cr-Commit-Position: refs/heads/master@{#27775}

BUG=chromium:339474
LOG=Y

Review URL: https://codereview.chromium.org/1002263004

Cr-Commit-Position: refs/heads/master@{#27205}

Add() becomes AddLocalExport, which takes an export_name and a local_name.
New parsing tests exercise this.

Also start generating exports for default exports (though this doesn't yet
handle anonymous default exports).

BUG=v8:1569
LOG=n

Review URL: https://codereview.chromium.org/934323004

Cr-Commit-Position: refs/heads/master@{#26758}