Subzero: Add missing content to CfgLocalAllocator.

The std::list<> implementation used by g++ needs some extra stuff defined in the custom allocator.

This can be smoke-tested with:

  make -f Makefile.standalone CXX=g++ LLVM_EXTRA_WARNINGS="-Wno-unknown-pragmas -Wno-unused-parameter -Wno-comment -Wno-enum-compare -Wno-strict-aliasing" STDLIB_FLAGS=

until the link fails for unrelated reasons.

BUG= https://code.google.com/p/nativeclient/issues/detail?id=4325
R=kschimpf@google.com

Review URL: https://codereview.chromium.org/1367403004 .