[LibFuzzer] Fix some unit test crashes on OSX.

This fixes the following unit tests:

FuzzerDictionary.ParseOneDictionaryEntry
FuzzerDictionary.ParseDictionaryFile

The issue appears to be mixing non-ASan-ified code (LibFuzzer) and
ASan-ified code (the unittest) as the tests would pass fine if
everything was built with ASan enabled.

I believe the issue is that different implementations of std::vector<>
are being used in LibFuzzer and outside LibFuzzer (in the unittests).
For Libcxx (I've not seen the issue manifest for libstdc++) we can disable
the ASanified std::vector<> by definining the ``_LIBCPP_HAS_NO_ASAN`` macro.
Doing this fixes the tests on OSX.

Differential Revision: http://reviews.llvm.org/D21049

llvm-svn: 272374