This fixes the parsing of git config options.
Be aware that you can use shell code in these options!
Thanks to Steffen Müthig for this fix!

If not found, our own fallback implementation will be used.

A previous commit introduced a check whether the element to-be-touched
is actually contained in the container.  That patch caused the test
to fail.  The new patch fixes this.

The two classes PushBackTuple and PushFrontTuple are both implemented
using a long list of template specializations.  This makes for a lot
of code, and it also limits the maximum tuple size that can be used.
Using variadic templates (FYI: available since gcc-4.3) instead
allows a generic implementation in only a few lines of code, and
only the compiler being the upper limit on tuple size.

An implementation using variadic templates has already been given
in the documentation of PushBackTuple/PushFrontTuple.  This patch
starts to actually use that implementation, provided that
HAVE_VARIADIC_TEMPLATES is set.  Otherwise the old implementation
is used.

MPICH has stepped up its versioning scheme, jumping from MPICH2 1.x
to MPICH 3.x, but has stayed compatible to the older MPICH2 versions.
Unfortunately, the macro MPICH2_VERSION used by mpi_config.m4 to detect
the package has been renamed to MPICH_VERSION.

This patch fixes the problem by adding a separate test for MPICH_VERSION
ana making sure that the macro starts with the letter "3".

It has been obsolete since Doxygen 1.8.1

Previously a value specified on the command line was always
overwritten by a value set in an options file. This patch
fixes this together with overwriting the build directory with
the default build-cmake when --use-cmake was specified.

Because the latter uses the C++11 standard library naming.

The C++11 standard library offers the functionality of SelectType,
it is, however, called 'conditional'.  This patch adds a copy
of our SelectType implementation with the class names changed
to match the ones used in C++11.  The old SelectType implementation
gets deprecated.

This fixes FS#1324.
Thanks to Arne Morten Kvarving for the patch.

- update documentation
- add paranoia check to touch()

update documentation

Previously, when adding boost flags, we always linked all
Boost_LIBRARIES. At least for the core modules this not needed
and resulted in errors on some systems.

This patch changes the add_dune_boost_flags function. By default no
libraries are linked, but one can either provide the libraries using
the LIBRARIES option or request linkage of all boost libraries with
the LINK_ALL_BOOST_LIBRARIES option.

Previously, if the user changed e.g. CMAKE_INSTALL_PREFIX or
CMAKE_INSTALL_DATAROOTDIR these changes where never mimiced in
DUNE_INSTALL_MODULEDIR. This patch fixes this problem, such that
DUNE_INSTALL_MODULEDIR changes unless it is explicitely set by the
user before.

We do using the same approach as in GNUInstallDirs.cmake. That is, we
whether DUNE_INSTALL_MODULEDIR is set to a non-empty string. If that
is the case we set an empty cache variable and overwrite locally with
the default value. The default value is now a relative path.

This fixes FS#1317 for me (use invert for 2x2 matrix with
std::complex< long double >).
The problem is that 1.0 is a double, which can be converted implicitly
to a long double which, in turn, could be converted implicitly into a
std::complex< long double >. However, the compiler does not use two
implicit type conversions, so double cannot be divided by a
std::complex< long double >.

See FS#1317 for details.

GNU xargs behaves differently from BSD xargs in that it always executes the command
at least once, even if there are no arguments on stdin.
As noticed by Martin, this behavior breaks the whitespace hook if the list of files to
be checked is empty. In that case, the hook will now check *all* staged changes, resulting
in false alarms.

So we test which version of xargs we have and use the correct flags in either case. If neither
one works, we bail out and ask the user to file a bug, but this behavior can be overriden with
the environment variable DUNE_WHITESPACE_IGNORE_XARGS.

Fixes FS#1316.