autoheader(1) on Linux

The text b9001d6d83f9, as Debian 7 (Wheezy), Debian 6.0 (Squeeze), Debian 5.0 (Lenny), Debian 4.0 (Etch), Debian 3.1 (Sarge) shipped it.

Wrapper for distinguishing Autoconf 2.13 and 2.50