detect the presence of std::shared_ptr

since GCC 4.4 supports it, make it mandatory as well...
use std::shared_ptr instead of boost::shared_ptr

our policy is that we only use boost if necessary, i.e., if the oldest
supported compiler does not support a given feature but boost
does. since we recently switched to GCC 4.4 or newer, std::shared_ptr
is available unconditionally.
add a few config.h macros useful for dune-common
also test for std::unique_ptr
replace boost::scoped_ptr by std::unique_ptr

thanks to Bård Skaflestad, Atgeirr Rasmusen and Roland Kaufmann for
the hint.
Merge pull request #313 from andlaus/use_std_shared_ptr

Use std shared ptr
add and use CMake modules for valgrind client requests and quadruple precision math
add test for <type_traits> to FindCXX11Features.cmake

I fogot this one yesterday...
add a cmake check for the abi::__cxa_demangle() function

this was also forgotten. sorry...
make the build system link to the "quadmath" library if it is supported

Thanks a lot to Roland Kaufmann for the support.
Merge pull request #315 from andlaus/checks_for_quadmath_and_valgrind

add and use CMake modules for valgrind client requests and quadruple precision math
Merge pull request #308 from rolk/308_agmg

Resurrect support for AGMG library

This is an interim milestone that may serve as point from which to 
resurrect the AGMG suppert fully if the AGMG author ever decides to 
re-release the software under an open licence.
Remove bindings to AGMG from library

AGMG is now under a closed-source license, meaning that results
obtained with this solver is not freely reproducible by others.
Its use is therefore discouraged.

As of version 2.3, the DUNE AMG parts are competitive, so there
is a free and open alternative.
Remove support for AGMG from the build system

AGMG is now under a closed-source license, meaning that results
obtained with this solver is not freely reproducible by others.
Its use is therefore discouraged.

As of version 2.3, the DUNE AMG parts are competitive, so there
is a free and open alternative.