As Carsten pointed out, the hash combining algorithms doesn't work
correctly for 32-bit platforms because it uses a multiplication with
a 64-bit constant.

This patch adds a switch for picking different algorithms based on the
size of std::size_t using a new struct hash_combiner that is templated
on the size of std::size_t.

Right now, there are implementations for 64-bit and 32-bit platforms,
both based on CityHash.

Previously a non existent file name (umfpack) was used in
Makefile.am. This broke the build with the message:

make[2]: *** Keine Regel vorhanden, um das Target »umfpack«,
  benötigt von »all-am«, zu erstellen.  Schluss.
make[2]: Leaving directory `/home/mblatt/src/dune/current/dune-common/build-auto/m4'

This patch fixes this by using the correct name.

This patch adds test for both CMake and autotools as the
build system.
UMFPack is used by several dune modules (e.g. fem and istl)
the only common required module by both is common. Therefore
we add the test here to make it usable for all modules.

BTW: These tests are taken from Dominics branch of dune-istl.
     Therefore he deserves the credit for them.

Fix generated config.cmake.in which contained a surplus endif.
List CMakeLists.txt and other files to be included in tarballs.
Move generated files around to sort them by directory.

Thanks to Tobias Malkmus for the heads-up.

Previously hidden unix files were included in the headercheck.
Unfortunately  emacs(server) tends to produces files such as
.#<headername>. This broke the constructed Makefiles. This patch
excludes such files from the list and fixes the issue.

This patch adds a new header visibility.hh with macros DUNE_EXPORT and DUNE_PRIVATE
to mark symbols as exported or private at the ABI level.

While we do not explicitly mark any symbols as hidden, there are certain situations
in which the compiler creates symbols with incorrect linkage, especially for singleton
accessor methods for templated types and their embedded static variables, which involve
the creation of weak symbols.

The linker is then unable to merge those weak definitions, causing either a link-time
failure (when building static libraries) or undefined runtime behaviour (dynamic libraries).

This problem can be avoided by explicitly marking the singleton accessor methods as
DUNE_EXPORT. For symmetry, there is also a DUNE_PRIVATE macro, but while it works, I don't
see it used very much in the short term.

We now check for METIS_PartGraphKway, which is a symbol that we are actually
using and which is also in the implementation of scotch (see FS#1370)

This patch removes an extra header install command for tests. It
originally came when copying dune/common/CMakeLists.txt to
dune/common/std/CMakeLists.txt. Sorry for the noise.

The majority of developers favor individual headers for (emulation of) C++11
features over collecting them in a single header cxx11.hh. This patch
renames cxx11.hh to constexpr.hh and moves it into the subdirectory std.
This is the place most developers would like these headers in (see
http://users.dune-project.org/doodles/4).

we are now checking for different locations of parmetis.h. This makes it possible us the
scotch parmetis implementation (see FS#1370).

we now check for METIS_PartGraphKway, which a symbol we are actually using and which
is in the implementation of scotch (see FS#1370)

Conflicts:
	cmake/modules/CheckCXX11Features.cmake

Avoid upper case commands.

They do not find a package but check for a feature.
This avoids false warnings about not found packages.
Merged FindCXX11Conditional.cmake and FindCXX11Features.cmake.

The patch from ...fce82c7d5ee5 broke the script.
This is the intended behavior.

As decided on the developer meeting in Aachen, we support (but do not
rely on) the C++11 keyword constexpr. This patch adds an m4-check for
constexpr and a header (cxx11.hh) defining a macro DUNE_CONSTEXPR either
as constexpr or empty (depending on the compiler support for it). It is
then used in FieldVector and FieldMatrix on size, rows, and cols.

Before this commit it matched e.g. "test1" and failed finding the directory "test".