DRTVWR-476: Remove throw(T) from operator new(), operator delete().

llcorehttp's test_allocator.{h,cpp} overrides global operator new(), operator
new[](), operator delete() and operator delete[](). The two operator new()
functions used to be declared with throw(std::bad_alloc). Worse, for VS 2013
and previous, we needed _THROW0() and _THROW1(std::bad_alloc) instead,
requiring #if logic.

But with dynamic throw declarations deprecated, we must actually remove those.
That obviates the THROW_BAD_ALLOC() / THROW_NOTHING() workarounds in
test_allocator.cpp.