Unify SMI case inlining for ToNumberStub.

Use ShouldInlineSmiCase() on arm, mips and x64 similar to the ia32 port.

R=dslomov@chromium.org

Review URL: https://codereview.chromium.org/19489003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15787 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Fix invalid SMI test in x64 ToNumberStub::Generate().

TBR=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/19927002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15788 ce2b1a6d-e550-0410-aec6-3dcde31c8c00