Fix KeyedAccessStoreMode on Windows

Fix KeyedAccessStoreMode on Windows

R=jkummerow@chromium.org

Committed: http://code.google.com/p/v8/source/detail?r=14189

[danno, 2013-04-09 16:10:21]

PTAL

[Jakob Kummerow, 2013-04-09 16:18:20]

LGTM with comment.

https://codereview.chromium.org/13812011/diff/1/src/ast.h
File src/ast.h (right):

https://codereview.chromium.org/13812011/diff/1/src/ast.h#newcode1814
src/ast.h:1814: KeyedAccessStoreMode store_mode_: 5;
Let's add a comment that an extra bit is needed because the Windows compiler
interprets packed bit fields as signed integers.

[danno, 2013-04-09 16:26:39]

Committed patchset #2 manually as r14189 (presubmit successful).