Decouple packages a bit more again: The prologue of the combined index is now
generated via shell magic from the package prologues. As a nice side effect,
some autoconf magic is gone, so configure.ac is effectively empty now (but not
for long... :-)
--- /dev/null
+This package contains the @Prelude@ and its support libraries, and a large
+collection of useful libraries ranging from data structures to parsing
+combinators and debugging utilities.