Introduce kRegisterSize, kPCOnStackSize and kFPOnStackSize constants

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15822 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Addressed danno's comments

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15823 ce2b1a6d-e550-0410-aec6-3dcde31c8c00