[CMake] Move the enable_all_packages feature to a separate module

The module DuneMacros.cmake is very crowded. Macros that are important
to end users and whose documentation should be clearly visible is
better placed in a separate file IMO. The new file is included from
DuneMacros.

cmake/modules/DuneEnableAllPackages.cmake

+# This module provides the macros necessary for a simplified CMake build system
+#
+# The dune build system relies on the user to choose and add the compile and link flags
+# necessary to build an executable. While this offers full control to the user, it
+# is an error-prone procedure.
+#
+# Alternatively, users may use this modules macros to simply add the compile flags for all
+# found external modules to all executables in a module. Likewise, all found libraries are
+# linked to all targets.
+#
+# This module provides the following macros:
+#
+# dune_enable_all_packages()
+#
+# Adds all flags and all libraries to all executables that are added in the directory
+# from where this macro is called and from all its subdirectories (recursively).
+# Typically, a user would add the call to this macro to his top level CMakeLists.txt
+
+macro(dune_enable_all_packages)
+  get_property(all_incs GLOBAL PROPERTY ALL_PKG_INCS)
+  include_directories(${all_incs})
+  get_property(all_libs GLOBAL PROPERTY ALL_PKG_LIBS)
+  link_libraries(${DUNE_LIBS} ${all_libs})
+  get_property(all_defs GLOBAL PROPERTY ALL_PKG_DEFS)
+  foreach(def ${all_defs})
+    add_definitions("-D${def}")
+  endforeach(def in ${all_defs})
+endmacro(dune_enable_all_packages)

cmake/modules/DuneMacros.cmake

@@ -79,6 +79,7 @@
 enable_language(C) # Enable C to skip CXX bindings for some tests.
 
 include(FeatureSummary)
+include(DuneEnableAllPackages)
 
 # Converts a module name given by _module into an uppercase string
 # _upper where all dashes (-) are replaced by underscores (_)
@@ -1155,15 +1156,3 @@ macro(add_dune_all_flags targets)
     target_link_libraries(${target} ${DUNE_LIBS} ${libs})
   endforeach()
 endmacro(add_dune_all_flags targets)
-
-# set includes, libraries and compile definitions for the entire project recursively
-macro(dune_enable_all_packages)
-  get_property(all_incs GLOBAL PROPERTY ALL_PKG_INCS)
-  include_directories(${all_incs})
-  get_property(all_libs GLOBAL PROPERTY ALL_PKG_LIBS)
-  link_libraries(${DUNE_LIBS} ${all_libs})
-  get_property(all_defs GLOBAL PROPERTY ALL_PKG_DEFS)
-  foreach(def ${all_defs})
-    add_definitions("-D${def}")
-  endforeach(def in ${all_defs})
-endmacro(dune_enable_all_packages)