Fix some valgrind errors in d8 shell.

Fix some valgrind errors in d8 shell.

This fixes 3 possibly lost warnings occurring when running unit tests under d8:

 28 bytes in 1 blocks are possibly lost in loss record 40 of 68
  at 0x67FB8DB: operator new[](unsigned int)
  by 0x83865CC: v8::Shell::SetOptions(int, char**) (d8.cc:1200)
  by 0x83869A5: v8::Shell::Main(int, char**) (d8.cc:1276)
  by 0x8386B31: main (d8.cc:1333)
Review URL: http://codereview.chromium.org/7780032

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@9252 ce2b1a6d-e550-0410-aec6-3dcde31c8c00