ids in generated xml

[Matthias Clasen <maclas gmx de>]

gtkdoc-mkdb contains CreateValidSGMLID which mangles ids in order to
meet the restrictions of typical sgml declarations. This is causing
problems when trying to use the ids for anything except linking within
gtk-doc produced material. I'm currently trying to convert dangling
links into man: urls, but this breaks e.g. for iconv_open(), which ends
up as <link linkend="iconv-open"> in the docbook. 

One could argue that functions with names not passing CreateValidSGMLID
unchanged are rare within standard C, but the fact remains that the
whole mangling is unnecessary when targetting XML. Thus I'd like to make
CreateValidSGMLID trivial if --output-format=xml. The only disadvantage
of this would be that links won't work between html produced from xml
and from sgml. 

Comments ?

Matthias