Generate documentation in a custom target

The targets are named after the similar targets when using Autotools.

CMakeLists.txt

@@ -229,3 +229,13 @@ configure_file (
 	${PROJECT_BINARY_DIR}/Doxyfile
 	@ONLY
 	)
+find_package (Doxygen)
+if (DOXYGEN_FOUND)
+	add_custom_target (doc
+		COMMAND ${DOXYGEN_EXECUTABLE} ${PROJECT_BINARY_DIR}/Doxyfile
+		SOURCES ${PROJECT_BINARY_DIR}/Doxyfile
+		WORKING_DIRECTORY ${PROJECT_BINARY_DIR}
+		COMMENT "Generating API documentation with Doxygen"
+		VERBATIM
+		)
+endif (DOXYGEN_FOUND)

Doxyfile.in

@@ -1528,7 +1528,7 @@ CLASS_DIAGRAMS         = YES
 # the mscgen tool resides. If left empty the tool is assumed to be found in the
 # default search path.
 
-MSCGEN_PATH            =
+MSCGEN_PATH            = @DOXYGEN_DOT_PATH@
 
 # If set to YES, the inheritance and collaboration graphs will hide
 # inheritance and usage relations if the target is undocumented
@@ -1654,7 +1654,7 @@ DOT_IMAGE_FORMAT       = png
 # The tag DOT_PATH can be used to specify the path where the dot tool can be
 # found. If left blank, it is assumed the dot tool can be found in the path.
 
-DOT_PATH               =
+DOT_PATH               = @DOXYGEN_DOT_PATH@
 
 # The DOTFILE_DIRS tag can be used to specify one or more directories that
 # contain dot files that are included in the documentation (see the