Clean up return statements in the code generator by explicitly...

Clean up return statements in the code generator by explicitly
counting the reference to the return value and passing it to the
return label.  This requires threading it through try/catch and
try/finally.  The return value is loaded into eax more lazily than
before.

Also, perform some related refactoring of jump targets.

Committed: http://code.google.com/p/v8/source/detail?r=1669

[Kevin Millikin (Chromium), 2009-04-02 08:13:31]

Fixed typos.

[Kasper Lund, 2009-04-02 08:19:08]

LGTM.