Embed orientation-restraint example in the doc

[update-doc]

doc/colvars-refman-main.tex

@@ -2504,16 +2504,32 @@
 
 \end{cvcoptions}
 
-\textbf{Tip: stopping the rotation of a protein.}  To stop the
+
+\paragraph*{Example: stopping the rotation of a protein.}  To stop the
 rotation of an elongated macromolecule in solution (and use an
 anisotropic box to save water molecules), it is possible to define a
 colvar with an \texttt{orientation} component, and restrain it through
 the \texttt{harmonic} bias around the identity rotation, \texttt{(1.0,
   0.0, 0.0, 0.0)}.  Only the overall orientation of the macromolecule
-is affected, and \emph{not} its internal degrees of freedom.  The user
-should also take care that the macromolecule is composed by a single
-chain, or disable \texttt{wrapAll} otherwise.
+is affected, and \emph{not} its internal degrees of freedom.  \cvnamdonly{In NAMD, the user
+should also take care that the macromolecule is composed by a single chain
+, or disable \texttt{wrapAll} otherwise.}
 
+\begin{cvexampleinput}
+\-colvar~\{\\
+\-~~name~Orient\\
+\-~~orientation~\{\\
+\-~~~~atoms~\{~\ldots~\}\\
+\-~~~~refPositionsFile~reference.pdb\\
+\-~~\}\\
+\-\}\\
+\-\\
+\-harmonic~\{~~~~~~~~~~~~~\#~Define~a~harmonic~restraint\\
+\-~~colvars~Orient~~~~~~~\#~acting~on~colvar~"Orient"\\
+\-~~centers~~(1.0,~0.0,~0.0,~0.0)~~\#~center~the~unit~quaternion~(no~rotation)\\
+\-~~forceConstant~500.0~~~~~~~~~~~~\#~unit~is~energy:~quaternions~are~dimensionless\\
+\-\}\\
+\end{cvexampleinput}
 
 
 \cvsubsubsec{\texttt{orientationAngle}: angle of rotation from reference coordinates.}{sec:cvc_orientationAngle}