Dear Maintainer,

I'm in the process of packaging several packages.
They're all development packages and form a chain, where each packages
documentation depends on the ones before.
After spotting that mm-common provides libstdc++.tag, I jumped on the chance to
use it.

In my configure.ac script I use
   MM_ARG_WITH_TAGFILE_DOC([libstdc++.tag],[mm-common-libstdc++])

I found some problems which I hope you can address.

1. mm-common recommends xsltproc, but MM_ARG_WITH_TAGFILE_DOC fails if it's not
installed.
   This should be a depends relation.
2. The resulting DOXYGEN_TAGFILES variable contains embedded quotes.
   I can fix this resiliently with sed.
3. The on-line html pages don't match the link names.
   For example, when I click on the "<string>" include file it takes me to the
<ctime> include file reference.

It would make more sense to refer to documentation on the standard library the
user has installed, not the latest version.

Regards,
Philip Ashmore