Add two more helper macros

Add a \transposon macro to typeset transposable elements, and a
\foreigngene macro to typeset non-Drosophila genes.

flygenet.dtx

@@ -94,7 +94,7 @@ has been generated for details.
 %
 % \changes{0.1}{2013/07/14}{Initial version.}
 % \changes{0.2}{2013/10/09}{Remove limitations.}
-% \changes{0.3}{2014/01/01}{Do not draw Y hook; add allele macro.}
+% \changes{0.3}{2014/01/01}{Do not draw Y hook; add some helper macros.}
 %
 % \GetFileInfo{flygenet.dtx}
 %
@@ -284,6 +284,23 @@ has been generated for details.
 %    \end{macrocode}
 % \end{macro}
 %
+% \begin{macro}{\transposon}
+% This macro represents a transposable elements. Its first argument
+% is the type of the transposon ends (e.g., ``P'' for a P-element), the
+% second is the list of genes or gene constructs inside the transposable
+% element.
+%    \begin{macrocode}
+\def\transposon#1#2{#1\{#2\}}
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\foreigngene}
+% This macro typesets a gene originating from a distinct species.
+%    \begin{macrocode}
+\def\foreigngene#1#2{#1\textbackslash #2}
+%    \end{macrocode}
+% \end{macro}
+%
 % \subsection{Gender symbols}
 %
 % \begin{macro}{\female}