docs: building documents without repository (form-dev#497)

Avoid typesetting errors even when there is no revision information from
the repository. The absence of revision information is indicated by
"???" appended to the version number shown on the title page of the
documents.

Author: tueda

doc/devref/devref.tex.in

@@ -2,7 +2,7 @@
 \def\formversiondesc{\repoversiondesc}
 \def\formdate{\repodate}
 %begin{latexonly}  % To avoid latex2html/latex2html#37
-\providecommand{\formversiondesc}{@VERSION@}
+\providecommand{\repoversiondesc}{@VERSION@???}
 \providecommand{\repodate}{\today}
 %end{latexonly}
 

doc/manual/manual.tex.in

@@ -4,7 +4,7 @@
 \def\formversiondesc{\repoversiondesc}
 \def\formdate{\repodate}
 %begin{latexonly}  % To avoid latex2html/latex2html#37
-\providecommand{\formversiondesc}{@VERSION@}
+\providecommand{\repoversiondesc}{@VERSION@???}
 \providecommand{\repodate}{\today}
 %end{latexonly}