Fix polymorphic inlined calls with migrating prototypes.

Fixed global object leak caused by overwriting the global receiver (the global proxy) in the global object with the global object itself (Chromium issue 324812).

Initialize Date parse cache with SMI instead of double to workaround sharing mutable heap numbers in snapshot (Chromium issue 280531).

Switch armv7 setting to arm_version==7 in v8 gyp files (Chromium issue 234135).

Performance and stability improvements on all platforms.

git-svn-id: http://v8.googlecode.com/svn/trunk@18311 ce2b1a6d-e550-0410-aec6-3dcde31c8c00