autogen.sh: call ./configure at the end

Most open source projects have the convention of
just running 3 commands to install in a system:
configuration, build, installation.

The first of these steps usually consists of running
./configure (if it's a tarball) *OR* autogen.sh (if
it's a git checkout) because autogen.sh normally
calls ./configure (if NOCONFIGURE is not set).

So then in general it is expected that calling
./autogen.sh --prefix=/foo in a git checkout
has the same effect as calling
./configure --prefix=/foo in a tarball, which
was not the case before this.
diff --git a/autogen.sh b/autogen.sh
index cb42321..ae7e6a1 100755
--- a/autogen.sh
+++ b/autogen.sh
@@ -59,5 +59,13 @@
     echo "Could not autoupdate config.sub and config.guess"
 fi
 
-echo "Finished!"
+if [ ! -z "$NOCONFIGURE" ]; then
+	echo "autogen.sh finished! ./configure skipped."
+	exit $?
+fi
 
+echo "autogen.sh finished! Now going to run ./configure $@"
+./configure $@ || {
+    echo "./configure failed";
+    exit 1;
+}