Build: Generate doxygen documentation in autogen.sh.

Another command line option (--no-doxygen) was added to disable
creating the doxygen documenation in cases where it not wanted or
if the doxygen tool is not installed.

autogen.sh

@@ -19,15 +19,38 @@ ${AUTOCONF:-autoconf}
 ${AUTOHEADER:-autoheader}
 ${AUTOMAKE:-automake} -acf --foreign
 
-# Generate the translated man pages if the "po4a" tool is available.
+# Generate the translated man pages and the doxygen documentation if the
+# "po4a" and "doxygen" tools are available.
 # This is *NOT* done by "autoreconf -fi" or when "make" is run.
-#
-# Pass --no-po4a to this script to skip this step. It can be useful when
-# you know that po4a isn't available and don't want autogen.sh to exit
-# with non-zero exit status.
-if test "x$1" != "x--no-po4a"; then
+# Pass --no-po4a or --no-doxygen to this script to skip these steps.
+# It can be useful when you know that po4a or doxygen aren't available and
+# don't want autogen.sh to exit with non-zero exit status.
+generate_po4a="y"
+generate_doxygen="y"
+
+for arg in "$@"
+do
+	case $arg in
+		"--no-po4a")
+			generate_po4a="n"
+			;;
+
+		"--no-doxygen")
+			generate_doxygen="n"
+			;;
+	esac
+done
+
+if test "$generate_po4a" != "n"; then
 	cd po4a
 	sh update-po
+	cd ..
+fi
+
+if test "$generate_doxygen" != "n"; then
+	cd doxygen
+	sh update-doxygen
+	cd ..
 fi
 
 exit 0