autoconf: Add autogen.sh from Xorg for easier setup from git
The defacto method to rebuild the autotools and run the generated
configure is an autogen.sh script. It is much more discoverable than the
custom `make configure' used here. The Makefile targets are still useful
for creating tarballs, though. This autogen.sh is copied from Xorg.
diff --git a/autogen.sh b/autogen.sh
new file mode 100755
index 0000000..19e5b55
--- /dev/null
+++ b/autogen.sh
@@ -0,0 +1,16 @@
+#! /bin/sh
+
+srcdir=`dirname "$0"`
+test -z "$srcdir" && srcdir=.
+
+SRCDIR=`(cd "$srcdir" && pwd)`
+ORIGDIR=`pwd`
+
+if test "x$SRCDIR" != "x$ORIGDIR"; then
+ echo "Mesa cannot be built when srcdir != builddir" 1>&2
+ exit 1
+fi
+
+autoreconf -v --install || exit 1
+
+"$srcdir"/configure "$@"