Serializer: support all alignment kinds.

Serializer: support all alignment kinds.

We use an alignment prefix for unusual alignment kinds (not kWordAligned).
This will cause new objects to be aligned in ReadObject, and back references
to be aligned to skip padding.

The motivation to change the undefined next sentinel in WeakCell is this:
When the deserializer aligns an object, it requires filler maps to already
exist to create filler objects as padding. However, deserializing the
filler map leads to deserializing NaN, which as heap number is aligned:
filler map > meta map > weak cell cache > undefined > NaN
If we use the-hole instead of undefined as sentinel, it works.

R=jochen@chromium.org,bbudge@chromium.org
BUG=v8:4178
LOG=N

Committed: https://crrev.com/2146ab75387d47eef6582bd8c2d0cfc6c42b68b6
Cr-Commit-Position: refs/heads/master@{#29044}

Committed: https://crrev.com/63f4c751625e6d9948ef2276ebacdd7fc7d916a6
Cr-Commit-Position: refs/heads/master@{#29047}

[jochen (gone - plz use gerrit), 2015-06-16 08:33:43]

lgtm

[Yang, 2015-06-16 08:39:45]

The CQ bit was checked by yangguo@chromium.org

[Yang, 2015-06-16 08:39:46]

The patchset sent to the CQ was uploaded after l-g-t-m from jochen@chromium.org
Link to the patchset: https://codereview.chromium.org/1179873003/#ps20001
(title: "add assertion")

[commit-bot: I haz the power, 2015-06-16 08:39:57]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1179873003/20001

[commit-bot: I haz the power, 2015-06-16 09:07:20]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-06-16 09:07:20]

Try jobs failed on following builders:
  v8_linux_dbg on tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_linux_dbg/builds/5739)

[Yang, 2015-06-16 09:23:52]

The CQ bit was checked by yangguo@chromium.org

[Yang, 2015-06-16 09:23:52]

The patchset sent to the CQ was uploaded after l-g-t-m from jochen@chromium.org
Link to the patchset: https://codereview.chromium.org/1179873003/#ps40001
(title: "fix assertion")

[commit-bot: I haz the power, 2015-06-16 09:24:01]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1179873003/40001

[commit-bot: I haz the power, 2015-06-16 09:46:02]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-06-16 09:46:20]

Patchset 3 (id:??) landed as
https://crrev.com/2146ab75387d47eef6582bd8c2d0cfc6c42b68b6
Cr-Commit-Position: refs/heads/master@{#29044}

[Michael Achenbach, 2015-06-16 10:18:15]

A revert of this CL (patchset #3 id:40001) has been created in
https://codereview.chromium.org/1173253006/ by machenbach@chromium.org.

The reason for reverting is: [Sheriff] Breaks arm debug compile:
http://build.chromium.org/p/client.v8/builders/V8%20Arm%20-%20debug%20builder....

[Yang, 2015-06-16 10:41:19]

The CQ bit was checked by yangguo@chromium.org

[Yang, 2015-06-16 10:41:19]

The patchset sent to the CQ was uploaded after l-g-t-m from jochen@chromium.org
Link to the patchset: https://codereview.chromium.org/1179873003/#ps60001
(title: "fix assertion conditional")

[commit-bot: I haz the power, 2015-06-16 10:41:26]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1179873003/60001

[commit-bot: I haz the power, 2015-06-16 11:04:19]

Committed patchset #4 (id:60001)

[commit-bot: I haz the power, 2015-06-16 11:04:31]

Patchset 4 (id:??) landed as
https://crrev.com/63f4c751625e6d9948ef2276ebacdd7fc7d916a6
Cr-Commit-Position: refs/heads/master@{#29047}