[asan] Fix Win64 test portability issues
The OOM test should really only run on 32-bits, since it's hard to OOM
The operator_array_new_with_dtor_left_oob tests need to account for the
larger array cookie on x64 (8 bytes instead of 4).
Use -std=c++14 in use-after-scope-capture.cc to avoid errors in the MSVC
2015 STL on Windows. The default there is C++14 anyway.