o Install original xhtml.soc as is.
o Install xhtml-dcl.soc file which has no SGMLDECL line.
o Register xhtml-dcl.soc as SGML catalog chain.
Users who use usual catalog file will not be affected, but if you
refer xhtml.soc directly and doesn't like SGMLDECL line, please use
xhtml-dcl.soc file instead.
