autoconf.texi node names with dots

[Kevin Ryde]

I noticed the autoconf index entries which have dots in the node names
don't work from emacs (21.1).  Eg. using "i" to find "CONFIG_COMMANDS"
ought to go to "Obsolete config.status Use" (from the Environment
Variables index), but gives an error

  No such anchor in tag table or node in tag table or file: Obsolete config

Though it might look like an emacs problem, the texinfo docs under
"Node Line Requirements" assert that a period is not allowed in a node
name.

Dunno what to do about it though, config.status is the name of the
script, and deserves to be referred to as such.