minor tidy-up to configury.

test/autogen.sh

@@ -1,11 +1,9 @@
 #!/bin/sh
 
-cp acinclude.m4 aclocal.m4
+set -e
 
-if test "$AUTOCONF"x = x; then
-  AUTOCONF=autoconf
-fi
+cp acinclude.m4 aclocal.m4
 
-$AUTOCONF || exit 1
+"${AUTOCONF:-autoconf}"
 rm aclocal.m4
 rm -rf autom4te.cache