We follow the advice of upstream and use only empty endif() and
else() statements in new code. The removal of the optional argument
is only in generated scripts.

Add missing files, remove ancient buildsystem stuff and stuff where it is
unclear where it comes from.

Some downstream modules like pdelab and dumux already abandoned the
current bahaviour of building tests on make test. The testing infrastructure
does throw them error messages during make test though. This commi introduces
the switch DUNE_DISABLE_TEST_MAGIC which may be set by downstream modules
to disable the magic. To see how to switch a downstream module, see:

http://conan2.iwr.uni-heidelberg.de/git/pdelab/dune-pdelab/commit/dc5ef4b39f5be5690457f0bbfe008b1f45d5fd98

This has to be done as each module puts dune-common_MODULE_PATH into
CMAKE_MODULE_PATH to find the DUNE's cmake macros. This should be removed
when building the complete CMAKE_MODULE_PATH module path (in reverse order
of the dependency). Unfortunately, the conditional to check whether
the variable dune-common_MODULE_PATH is set was incorrect. This commit fixes
this.

I hope that this fixes FS 1686
https://dune-project.org/flyspray/index.php?do=details&task_id=1686

Please merge to the release

Commit 4878943f actuall did change
the default behavior, it effectifly disabled LaTex for some users.
To disable LaTeX pass -DCMAKE_DISABLE_FIND_PACKAGE_LATEX=TRUE

Otherwise it collides with the config.h.cmake for in-source builds.
The generated file is called config_collected.h.cmake.
Thanks to Robert for the heads-up.

Setting a policy must be guarded as older CMake version do not
know about the policy.

CMake >= 2.8.12 can optionally use @rpath to embed dynamic linker paths
into shared libraries on OS X. This greatly improves reliability with
libraries in non-standard locations and should definitely be turned on
by default.

script. This feature is disabled by default and can be enabled by
-DALLOW_CXXFLAGS_OVERWRITE=ON.

All the functionality in DuneEnableAllPackages.cmake is now contained in
functions instead of macros. Update the documentation to reflect that.

State the minimum required version of CMake in the documentation for
dune_enable_all_packages() and dune_target_enable_all_packages().

dune_enable_all_packages has to update the compiler options, but the
command compile_options only exists in CMake 2.8.12+. So we add a hard
requirement for that CMake version to the function.

I only ever intended this feature to work for CMake >= 2.8.12, so this
doesn't really change anything, except for giving the users a more
useful diagnostic.

Minimum required CMake version is 2.8.12 and not 2.9.12.

The duncontrol / dune.module mechanism allowes to overload the run_* commands, which
are executed in order to setup/build/etc. a module. This patch fixes a bug in the cmake
parsing of the dune.module file. Somehow cmake tried to interpret the content of the
dune.module as cmake code. We now use a different strategy to parse the file and avoid
storing the content in a temporary variable.

>> please backport to 2.4

BOOST_FOUND seems to be no longer known, use
HAVE_DUNE_BOOST instead.

Affected are older CMake versions 2.8.6 to 2.8.9 maybe even,
newer versions.

dune_library_add_sources() verifies the library name against the
contents of DUNE_ENABLE_ALL_PACKAGES_MODULE_LIBRARIES. I accidentally
broke this by converting dune_enable_all_packages (which defines the
variable) from a macro to a function, which removed the variable from
global scope.

This patch fixes the problem by explicitly exporting the variable to the
parent scope, making it available to dune_library_add_sources() again.

We have to call add_definitions() in a loop because add_definitions() is
kind of broken: even though it is supposed to be *the* function for
adding compile definitions, it does not prepend "-D" (as opposed to
target_compile_definitions(), which does). Well, whatever...

Thanks for spotting that, Dominic!

We do not really support this combination of C++11 features, and the
only time it should occur is when the user has a recent Intel Compiler
and an outdated GCC (which the Intel Compiler uses for the C++ standard
library). In that case, we emit a helpful error message at configuration
time.

This patch adds a new function dune_target_enable_all_packages() that
works like dune_enable_all_packages(), but only acts on the given list
of targets.

This function is mostly needed to be able to use the new
dune_enable_all_packages() feature in a DUNE module that defines its own
libraries. Specifically, the "nice" default way of handling those
libraries only works on CMake 3.1+. To be compatible with older CMake
versions, the library has to be manually added in the top-level
CMakeLists.txt file before the call to dune_enable_all_packages(). But
the library also needs to get all the package flags from the DUNE
modules the current one depends on, which can be done using the new
function added by this patch.

All of the macros in DuneEnableAllPackage cause their side effects by
modifying properties, so there is no point in having them as macros,
which are more fragile than functions and pollute the outside variable
scope.

- Fix some typos
- Improve wording
- Try to be clearer about the distinction between CMake modules and DUNE
  modules

on Ubuntu.

Passing multiple files to dune_symlink_to_source_files() was broken.
While at it, I switched the given macros to be functions and have
named arguments. Using positional arguments will result in a warning.

For discussion check FS1648.

Disabling a cmake module through CMAKE_DISABLE_FIND_PACKAGE_...
was only partially working:
- Any module suggesting the disabled module would not search for it
- dunecontrol did not have this knowledge and built the disabled module nevertheless

This commit fixes the latter.

The test for __cxa_demangle(), which is used by Dune::className() to
demangle type names, doesn't work on my clang 3.6. Apparently, clang
requires the user to include <typeinfo> before <cxxabi.h>. While
classname.hh already does this, the build system tests don't, causing the
feature to get disabled on clang.

Fixed by adding the include to the build system tests.