In automake 1.11 the index node name for its autoconf macros is now
"Macro Index", split from what was a combined "Macro and Variable
Index".  Adding it along the lines below allows macros like
AM_INIT_AUTOMAKE to be found from C-h S in autoconf-mode,

2011-05-11  Kevin Ryde  <user42@zip.com.au>

	* info-look.el (autoconf-mode): Add "(automake)Macro Index" for
	automake 1.11 macros.  Add "(automake)Index" for automake 1.3
	macros.