Localized docs are broken structurally

[strk]

Running make -C doc check-localized shows many errors in multiple languages.

Example:

make[2]: Entering directory '/home/src/postgis/postgis/doc/po/pt_BR'
/usr/bin/perl -lpe "s'@@LAST_RELEASE_VERSION@@'3.3.0dev'g;s'@@POSTGIS_DOWNLOAD_URL@@'http://postgis.net/stuff'g;" postgis.xml > postgis-out.xml
/usr/bin/xsltproc --novalid --path . xsl/postgis_aggs_mm.xml.xsl postgis-out.xml > postgis_aggs_mm.xml
/usr/bin/xmllint --loaddtd --path . --xinclude --valid postgis-out.xml > /dev/null
reference_management.xml:557: element funcprototype: validity error : Element funcprototype content does not follow the DTD, expecting (modifier* , funcdef , (void | varargs | (paramdef+ , varargs?)) , modifier*), got (funcprototype funcprototype )
> </funcprototype>
                  ^