Simplify installing concurrently recompiled code.

Instead of overwriting the code entry of the function, we trigger
an interrupt to install the code on the main thread.

R=mstarzinger@chromium.org
BUG=

Review URL: https://codereview.chromium.org/23542029

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16681 ce2b1a6d-e550-0410-aec6-3dcde31c8c00