Fix %NeverOptimizeFunction runtime call.

Fix %NeverOptimizeFunction runtime call.

The current usage of this runtime function is broken as it does not
prevent inlining of the affected function but rather bails out from the
whole unit of compilation after trying to inline affected functions.
This simplifies said runtime function to avoid accidental misuse.

R=titzer@chromium.org
TEST=mjsunit/never-optimize

Review URL: https://codereview.chromium.org/19776006

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15762 ce2b1a6d-e550-0410-aec6-3dcde31c8c00