doc: stop generating defines.texi from configure

* generating defines.texi from configure means quagga.info will always have
  to be rebuilt by end-users, even from dist tarballs. Also breaks
  distcheck assumptions that info won't need to be built - which can be
  fixed with 'info-in-builddir' automake option, but that's too recent
  to rely on.
* doc/defines.texi.in: nuke
* doc/defines.texi: Add static version.
* {doc/Makefile.am,configure}: nuke autogen of above
* doc/quagga.texi: remove the 1 use of PACKAGE_STRING
diff --git a/doc/quagga.texi b/doc/quagga.texi
index bcf23de..3e21cf8 100644
--- a/doc/quagga.texi
+++ b/doc/quagga.texi
@@ -70,7 +70,7 @@
 		     
 @uref{http://www.quagga.net,,Quagga} is an advanced routing software package
 that provides a suite of TCP/IP based routing protocols.  This is the Manual
-for @value{PACKAGE_STRING}. @uref{http://www.quagga.net,,Quagga} is a fork of 
+for Quagga @value{VERSION}. @uref{http://www.quagga.net,,Quagga} is a fork of 
 @uref{http://www.zebra.org,,GNU Zebra}.
 
 @insertcopying