DOC: Define \itkref and \itksubref Doxygen reference macros

Companion to InsightSoftwareConsortium/ITK#6416, which renames the
\doxygen/\subdoxygen spellings in the ITK Software Guide example
blocks. The old names remain as aliases for ITK branches that still
use them.

Author: hjmjohnson

SoftwareGuide/SoftwareGuideConfiguration.tex.in

@@ -15,13 +15,18 @@
 \itkFullVersiontrue
 
 % Define command to make reference to on-line Doxygen documentation
-\newcommand{\doxygen}[1]{
+\newcommand{\itkref}[1]{
 \href{https://www.itk.org/Doxygen/html/classitk_1_1#1.html}{\code{itk::#1}}}
 
 % Define command to make reference to on-line Doxygen documentation
-\newcommand{\subdoxygen}[2]{
+\newcommand{\itksubref}[2]{
 \href{https://www.itk.org/Doxygen/html/classitk_1_1#1_1_1#2.html}{\code{itk::#1::#2}}}
 
+% Deprecated spellings of \itkref / \itksubref, kept for ITK branches that
+% still use them in their Software Guide example blocks.
+\newcommand{\doxygen}[1]{\itkref{#1}}
+\newcommand{\subdoxygen}[2]{\itksubref{#1}{#2}}
+
 % Define command for the standard comment introducing classes with similar functionalities
 \newcommand{\relatedClasses}{
 \textbf{The following classes provide similar functionality:}}