PPC: Add a MathFloor stub generated with TurboFan

PPC: Add a MathFloor stub generated with TurboFan

Port abc35080b33cc31e47b9913e64ac99ec687c6b65

Original commit message:
This stub will be used as the basis of a Math.floor-specific CallIC to
detect and track calls to floor that return -0.

Along the way:
- Create a TurboFanCodeStub super class from which the StringLength and
MathRound TF stubs derive.
- Fix the ugly hack that passes the first stub parameter as the "this"
pointer in the the TF-compiled JS function.
- Fix bugs in the ia32/x64 disassembler.

R=danno@chromium.org, dstence@us.ibm.com, michael_dawson@ca.ibm.com
BUG=

Committed: https://crrev.com/58c40db2558050c21648ff19d0e1f4b3b9297527
Cr-Commit-Position: refs/heads/master@{#28341}

[dstence, 2015-05-11 14:10:47]

lgtm

[MTBrandyberry, 2015-05-11 14:10:54]

The CQ bit was checked by mbrandy@us.ibm.com

[commit-bot: I haz the power, 2015-05-11 14:11:03]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1137033002/1

[commit-bot: I haz the power, 2015-05-11 14:33:34]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-05-11 14:33:47]

Patchset 1 (id:??) landed as
https://crrev.com/58c40db2558050c21648ff19d0e1f4b3b9297527
Cr-Commit-Position: refs/heads/master@{#28341}