Arm support for DoubleToIStub (truncating).

Added support for truncating DoubleToIStub and reorganize the macro-assembler
dToI operations to do the fast-path inline and the slow path by calling the
stub.

BUG=
R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/23129003

Patch from Ross McIlroy <rmcilroy@google.com>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16322 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Store mode for keyed stores should be passed in from type feedback
regardless of the map used in polymorphic stores.

BUG=
R=jkummerow@chromium.org, verwaest@chromium.org

Review URL: https://codereview.chromium.org/21058003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16323 ce2b1a6d-e550-0410-aec6-3dcde31c8c00