Fix two deallocation bugs identified by Coverity Prevent.

Fix two deallocation bugs identified by Coverity Prevent.

1. The tables array allocated in the CompilationSubCache constructor
   was never deallocated.  Fixed by adding destructor.

2. The buffer allocated in one of the constructors of the
   NoAllocationStringAllocator was never deallocated.  It seems that
   this class sometimes owns the buffer (if it allocated one itself)
   and sometimes doesn't (if it was passed one).  Simple fix is to
   remove the offending constructor which was never used anyway.

Review URL: http://codereview.chromium.org/155917

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2520 ce2b1a6d-e550-0410-aec6-3dcde31c8c00