Some people might have stray acinclude.m4's lying around in their build dir so let's delete them.

Original commit message from CVS:
Some people might have stray acinclude.m4's lying around in their build dir
so let's delete them.
For those that wondered : yes, I ran make distcheck on an anonymous checkout.
This would've helped Zeenix.
Let me know if you think this is the wrong solution.
diff --git a/autogen.sh b/autogen.sh
index 2252f3d..813ba6b 100755
--- a/autogen.sh
+++ b/autogen.sh
@@ -45,6 +45,7 @@
 
 toplevel_check $srcfile
 
+if test -e acinclude.m4; then rm acinclude.m4; fi
 tool_run "aclocal" "-I common/m4 $ACLOCAL_FLAGS"
 
 # FIXME : why does libtoolize keep complaining about aclocal ?