swift234

Fix leak of std::function in NominalTypeDecl::DelayedMembers

We were memcopying a std::function into the the AST context memory,
which leaks memory incidentally used by the std::function
implementation.  Fix by using a std::unique_ptr and registering a
destructor cleanup.  Incidentally, I turned the array of functions into
a single function, since we never have more than one anyway.

rdar://problem/22387897

Swift SVN r31600