Shrink-wrap UnlinkedCodeBlock members.
<http://webkit.org/b/109368>

Reviewed by Oliver Hunt.

Rearrange the members of UnlinkedCodeBlock to avoid unnecessary padding on 64-bit.
Knocks ~600 KB off of the Membuster3 peak.

* bytecode/UnlinkedCodeBlock.cpp:
(JSC::UnlinkedCodeBlock::UnlinkedCodeBlock):
* bytecode/UnlinkedCodeBlock.h:
(UnlinkedCodeBlock):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@142387 268f45cc-cd09-0410-ab3c-d52691b4dbfc