Added missing \+ command to build LaTeX manual

doc/doxygen_manual.tex

@@ -51,6 +51,7 @@
 \usepackage[titles]{tocloft}
 \usepackage{amssymb}
 \usepackage{doxygen}
+\newcommand{\+}{\discretionary{\mbox{\scriptsize$\hookleftarrow$}}{}{}}
 \lstset{language=C++,inputencoding=utf8,basicstyle=\footnotesize,breaklines=true,breakatwhitespace=true,tabsize=8,numbers=left }
 \makeindex
 \setcounter{tocdepth}{3}