Set up trivial configure test for Hinnant's unique_ptr.

This involved several steps:
* Use the new AM_CONDITIONAL in appropriate Makefile.ams
* Allow user to explicitly disable with --disable-hinnant-unique-ptr
* Add conditional installation flags for Howard Hinnant's unique_ptr
  to script which builds Makefile.ams
* Regenerate Makefile.am using said script
* Adding a libmesh_config #define for Howard Hinnant's unique_ptr
Ran bootstrap
Only include unique_ptr.hpp if configure tested/found it.

Fixing preprocessor token for C++11 std::unique_ptr
Adding back the original libmesh AutoPtr class, now renamed DeprecatedAutoPtr.

This class will the third fallback if neither std::unique_ptr or boost::unique_ptr
are available.
The std::unique_ptr spec defines a swap() member function, the
original std::auto_ptr spec did not.

We could enchance the DeprecatedAutoPtr interface, but I think it's
wiser to just leave that be and use functionality available in both
classes.
Adding a configure test to ensure the compiler can actually compile unique_ptr.hpp

Main difficulty is getting the right CXXFLAGS while using either an external Boost or libmesh's Boost.
Ran bootstrap