RecordWriteStubs on ARM need to save FP registers

RecordWriteStubs on ARM need to save FP registers

A previous change erroneously stopped saving fp registers for write stubs in
snapshotted code. This CL restores correct behavior, and makes sure code that
saves fp registers checks at runtime for 16 or 32 fp registers. Also fix a bug
in the arm simulator debugger.


BUG=

Committed: https://code.google.com/p/v8/source/detail?r=14359

[mvstanton, 2013-04-19 13:22:33]

Hi guys,
Here is the 
1) revert of the erroneous arm fp reg change from yesterday (thx for catching,
Paul)
2) now check at runtime in record write stubs how many ARM registers we have,
using snazzy vldm/vstm instructions.
3) Touch another place that saves fp registers, using vldm/vstm.
4) Code appearing soon in the snapshot needs StoreBufferOverflowStub with
kSaveFPRegs mode.

[mvstanton, 2013-04-19 15:47:38]

Thanks for the good review Ulan, here are my updates.

[ulan, 2013-04-19 15:52:42]

LGTM

[Michael Starzinger, 2013-04-19 15:53:42]

LGTM.

[mvstanton, 2013-04-19 16:02:06]

Committed patchset #2 manually as r14359 (presubmit successful).