Report deoptimization error in release mode.

This makes sure that we crash and burn in release mode in cases where
the deoptimizer is unable to find the PC offset into unoptimized code
during deoptimization. So far this failure got swallowed in production.

R=ulan@chromium.org
BUG=chromium:159140

Review URL: https://codereview.chromium.org/11451033

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13148 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/deoptimizer.cc

@@ -546,7 +546,7 @@ int Deoptimizer::GetOutputInfo(DeoptimizationOutputData* data,
   shared->SourceCodePrint(&stream, -1);
   PrintF("[source:\n%s\n]", *stream.ToCString());
 
-  UNREACHABLE();
+  FATAL("unable to find pc offset during deoptimization");
   return -1;
 }