Rename the kinds of locations to be consistent with the (codegen)...

Rename the kinds of locations to be consistent with the (codegen)
context of the expressions they label.  Introduce an "unintialized"
location to catch failure to assign any location at all.

Changed the object literal initialization on ARM to use a Store IC in
the same cases where it did on the other platforms.  This was required
because the location of the literal property name is given an
"unitialized" location.

[Kevin Millikin (Chromium), 2009-10-28 15:22:13]

We should decide what location we want to assign to the literals that we don't
visit in the backend.  Unitialized seems good, because it traps most attempts to
use them as if they'd been visited.

[William Hesse, 2009-10-28 15:28:53]

LGTM.

[fschneider, 2009-10-28 16:46:39]

LGTM.