simplify OpenBSD case by using arch(1) and sed to grab
the machine architecture. We now output amd64 instead
of x86_64 as it should be.

ok deraadt@ pvalchev@

shared files for gnu configure:
- cygnus configure
- libtool files
- config.guess, config.if, config.sub
- mkdirs.sh, install-sh, move-if-change