Split autogen.sh into autopull.sh and autogen.sh.

* autopull.sh: New file, based on autogen.sh.
* autogen.sh: Remove code that was moved to autopull.sh.
* Makefile.in (SOURCE_FILES): Add autogen.sh.

Makefile.in

@@ -61,7 +61,7 @@ maintainer-clean : force
 # List of source files.
 SOURCE_FILES = \
   README INSTALL.windows NEWS AUTHORS JOIN-GNU \
-  configure.ac aclocal.m4 Makefile.in \
+  autogen.sh configure.ac aclocal.m4 Makefile.in \
   Makefile.devel ChangeLog
 # List of distributed files imported from other packages.
 IMPORTED_FILES = \