Adding standard autoconf test macro for determing C++11 support flag.

@roystgnr your name is on the author's list for this file, yet we
weren't using it in libmesh?!
Adding configure tests for C++11 features

* std::move
* std::shared_ptr
Only compile std::move code in fparser if the compiler supports it
Ran bootstrap.
GCC 4.6.3 does support -std=c++0x, but it doesn't support override.

So make the new configure test a bit less stringent.  This test is a
little tricky to get right -- it has to have *some* C++11 stuff to
accurately determine what the correct flag for turning on C++11
support is, but it can't test lots of features otherwise C++11 will
sometimes be disabled completely without good reason.
Fix a make_pair call in nanoflann.
Allow user to explicitly disable C++11 support.

Also, no more explicit setting of -std=c++0x for some compilers.
Ran bootstrap.
Merge pull request #285 from libMesh/cxx11

Add -std=c++11 to CXXFLAGS by default, test for some specific C++11 features