fix(util/memory): redefine the non-throwing versions of the new
operator.

In some platforms, the following operator new is used

   void* operator new(std::size_t sz, std::nothrow_t const &)

Since, it was not defined by memory.cpp, a crash would happen whenever
our delete was invoked.

   void  operator delete(void * ptr) throw() { return lean::free(ptr); }

Our delete assumes the memory was allocated with our new at memory.cpp

   void* operator new(std::size_t sz)
checkpoint

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>