[macros] Make xref hack work with newer memoir class (#6890)

Author: jensmaurer

source/macros.tex

@@ -78,12 +78,12 @@
 
 % Set the xref label for a clause to be "Clause n", not just "n".
 \makeatletter
-\newcommand{\customlabel}[2]{%
-\@bsphack \begingroup \protected@edef \@currentlabel {\protect \M@TitleReference{#2}{\M@currentTitle}}\MNR@label{#1}\endgroup \@esphack%
+\newcommand{\customlabel}[3]{%
+\@bsphack \protected@write\@auxout{}{\string\newlabel{#1}{{#3}{\thepage}{}{#2.\thechapter}{}}} \@esphack%
 }
 \makeatother
-\newcommand{\clauselabel}[1]{\customlabel{#1}{Clause \thechapter}}
-\newcommand{\annexlabel}[1]{\customlabel{#1}{Annex \thechapter}}
+\newcommand{\clauselabel}[1]{\customlabel{#1}{chapter}{Clause \thechapter}}
+\newcommand{\annexlabel}[1]{\customlabel{#1}{appendix}{Annex \thechapter}}
 
 % Use prefix "Annex" in the table of contents
 \newcommand{\annexnumberlinebox}[2]{Annex #2\space}