Define a constructor for nothrow_t.
Define a constructor for nothrow_t.

If we don't define a constructor clang++ complains:

  kernel/cpprt.cc:13:27: error: default initialization of an object of const type
        'const std::nothrow_t' requires a user-provided default constructor

aclements/sv6,bowlofstew/sv6,aclements/sv6,aclements/sv6,bowlofstew/sv6,aclements/sv6,bowlofstew/sv6,bowlofstew/sv6,aclements/sv6,bowlofstew/sv6