Squashed 'cmake/' content from commit 07b56b6

git-subtree-dir: cmake
git-subtree-split: 07b56b6a3dbe9f0c15160b3d11f11702db5e3999

Modules/ProcessDOXYGEN.cmake

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+INCLUDE(CheckParent)
+
+IF(NOT hasParent)
+  find_package(Doxygen)
+
+
+  IF (DOXYGEN_FOUND)
+    # set input and output files
+    set(DOXYGEN_IN ${CMAKE_CURRENT_SOURCE_DIR}/docs/Doxyfile.in)
+    set(DOXYGEN_OUT ${CMAKE_CURRENT_BINARY_DIR}/Doxyfile)
+
+    # request to configure the file
+    configure_file(${DOXYGEN_IN} ${DOXYGEN_OUT} @ONLY)
+
+    # note the option ALL which allows to build the docs together with the application
+    add_custom_target( doxygen
+        COMMAND ${DOXYGEN_EXECUTABLE} ${DOXYGEN_OUT}
+        WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
+        COMMENT "Generating API documentation with Doxygen"
+        VERBATIM )
+  ENDIF()
+
+ENDIF()