new: BB_ENABLE_DOXYGEN (copied from cppunit)

define AM_CONDITIONAL DOX if Doxygen is available

acinclude.m4

@@ -635,3 +635,38 @@ AC_SUBST(LDSHARED)
 dnl End of loadable modules determination
 ]) dnl AC_MODULES_INFO
 
+dnl stolen from cppunit project (http://cppunit.sourceforge.net/)
+AC_DEFUN(BB_ENABLE_DOXYGEN,
+[
+AC_ARG_ENABLE(doxygen, [  --enable-doxygen        enable documentation generation with doxygen (auto)])
+AC_ARG_ENABLE(dot, [  --enable-dot            use 'dot' to generate graphs in doxygen (auto)])              
+AC_ARG_ENABLE(html-dox, [  --enable-html-dox      enable HTML generation with doxygen (yes)], [], [ enable_html_dox=yes])              
+AC_ARG_ENABLE(latex-dox, [  --enable-latex-dox     enable LaTeX documentation generation with doxygen (no)], [], [ enable_latex_dox=no])              
+if test "x$enable_doxygen" = xno; then
+        enable_dox=no
+else 
+        AC_PATH_PROG(DOXYGEN, doxygen, , $PATH)
+        if test "x$DOXYGEN" = x; then
+                if test "x$enable_doxygen" = xyes; then
+                        AC_MSG_ERROR([could not find doxygen])
+                fi
+                enable_dox=no
+        else
+                enable_dox=yes
+                AC_PATH_PROG(DOT, dot, , $PATH)
+        fi
+fi
+AM_CONDITIONAL(DOX, test x$enable_dox = xyes)
+
+if test x$DOT = x; then
+        if test "x$enable_dot" = xyes; then
+                AC_MSG_ERROR([could not find dot])
+        fi
+        enable_dot=no
+else
+        enable_dot=yes
+fi
+AC_SUBST(enable_dot)
+AC_SUBST(enable_html_dox)
+AC_SUBST(enable_latex_dox)
+])